Cheesy Spinach Baked Spaghetti

Baked Spaghetti with Spinach and Mushrooms: A Florentine Delight

There’s something uniquely comforting about a classic pasta bake, and this Baked Spaghetti with Spinach and Mushrooms elevates that feeling to a whole new level. It has always held a special place in my heart, a cherished family recipe passed down through generations. My mother, with her culinary wisdom, often prepared extra spaghetti when making her incredible homemade spaghetti sauce, specifically reserving the excess pasta to transform it into this cheesy, spinach-infused delight. And I must admit, I’ve always preferred this innovative Florentine twist over the traditional version.

What’s not to adore? Imagine perfectly cooked spaghetti, baked until it achieves a delightful crispiness around the edges, enveloped in a creamy, luxurious blend of cheeses. This is beautifully complemented by the earthy depth of sautéed mushrooms and the fresh, vibrant notes of spinach, all baked together into a bubbling, golden-brown casserole that promises warmth and satisfaction. It’s a dish that truly sings, and I’m confident you’ll find it just as irresistible as I do.

Baked spaghetti, at its core, embodies the essence of comfort food. It’s simple, honest, and profoundly satisfying. This particular recipe shines as a hearty meatless main dish, providing ample protein and nutrients, or it can serve as a robust and flavorful side dish to complement your favorite entrées. Its preparation is surprisingly straightforward, especially if you wisely utilize leftover pasta, making it an ideal choice for a comforting meal without extensive effort. It’s a testament to how simple ingredients, combined with a little love and oven magic, can create something truly extraordinary.

Ingredient Spotlight: Crafting Your Perfect Baked Spaghetti

The magic of this baked spaghetti with spinach lies in the quality and balance of its ingredients. Here’s a detailed look at what you’ll need and some tips for selection:

• Spaghetti: The foundation of our casserole. Feel free to choose your preferred brand; however, for a more nutritious and wholesome option, I highly recommend using whole wheat spaghetti. It adds a subtle nutty flavor and a satisfying texture that stands up beautifully to the baking process. You’ll need approximately 8 ounces, which is half of a standard one-pound box. This recipe is also a fantastic way to revitalize any leftover cooked spaghetti you might have on hand. While spaghetti is traditional, don’t hesitate to experiment with other pasta shapes like penne, ziti, or rotini; most medium-sized pasta varieties will work wonderfully in this bake, ensuring every bite is loaded with flavor.
• Mushrooms: Regular white button mushrooms are perfectly suitable and widely available. For an added layer of flavor and texture, consider using cremini (baby bella) mushrooms, which offer a slightly deeper, earthier taste. To save precious time during prep, look for pre-sliced mushrooms at your grocery store. Their quick sautéing process helps release their umami, enriching the overall taste of the dish.
• Onion and Garlic: These aromatic staples form the flavor base of our casserole. Simple yellow cooking onions and fresh garlic cloves are all you need. When sautéed, they become sweet and fragrant, creating a savory foundation that profoundly enhances the natural flavors of the spinach and pasta. Their presence is subtle yet crucial for a well-rounded taste.
• Spinach: For convenience and consistent results, a 10-ounce package of frozen chopped spinach is recommended. The most critical step when using frozen spinach is to thaw it completely and then meticulously squeeze out all excess moisture. This prevents the casserole from becoming watery and ensures a rich, concentrated spinach flavor.
• Egg, Sour Cream, and Milk: This creamy trio plays a vital role in binding all the elements of the casserole together, creating a luxurious, custardy texture that holds the dish beautifully. The egg acts as a binder, while the sour cream and milk contribute to the overall richness, moisture, and creamy consistency, ensuring that the spaghetti doesn’t dry out during baking.
• Monterey Jack Cheese and Parmesan Cheese: These two cheeses are chosen for their excellent melting properties and distinct flavors. Monterey Jack melts beautifully, providing a gooey, mild, and creamy texture. Parmesan adds a sharp, salty, and umami-rich punch. While this combination is fantastic, feel free to explore other cheese types. Swiss cheese, with its slightly nutty profile, pairs exceptionally well with spinach and nutmeg. Gruyere or even a mild provolone could also be delicious alternatives, allowing you to customize the cheesy goodness to your preference.
• Nutmeg, Salt, and Pepper: These simple seasonings are likely already in your spice cabinet, but their impact is significant. Nutmeg, in particular, has a classic affinity for spinach, lending a warm, subtly sweet, and aromatic note that truly elevates the dish. I personally prefer freshly grated nutmeg when possible, as its flavor is notably more potent and vibrant than pre-ground varieties, offering a more aromatic depth to the casserole. Kosher salt and freshly ground black pepper tie all the flavors together, seasoning the vegetables and the creamy sauce perfectly.

Step-by-Step Guide: How to Assemble Your Baked Spaghetti Casserole

Creating this delicious baked spaghetti is a rewarding process. Follow these detailed steps to ensure a perfectly cheesy and comforting casserole:

1. Cook the Spaghetti: Begin by placing a large pot of water on your stove and bringing it to a rolling boil. Once boiling, add your spaghetti and cook it according to the package directions until it is al dente – tender yet still firm to the bite. Once cooked, drain the spaghetti thoroughly and set it aside. If you’re using leftover cooked pasta, you can conveniently skip this step entirely and proceed to the next.

2. Prepare for Baking: While your pasta is cooking, preheat your oven to 350°F (175°C). Locate a 1 ½ quart casserole or baking dish and lightly grease it or spray it generously with non-stick cooking spray. This will prevent the cheesy spaghetti from sticking and ensure easy cleanup.

3. Sauté the Aromatics: Simultaneously, as the pasta cooks, begin your vegetable prep. Shred your Monterey Jack and Parmesan cheeses, and finely chop the mushrooms, onions, and mince the garlic. Heat one tablespoon of olive oil in a skillet over medium-high heat. Add the sliced mushrooms and chopped onions, sprinkling them with ½ teaspoon of kosher salt and ¼ teaspoon of black pepper. Sauté for about 6 to 7 minutes, stirring occasionally, until the mushrooms are beautifully golden brown and the onions have softened and become translucent. Next, add the minced garlic to the skillet and cook for just one minute more, stirring constantly, until fragrant. Be careful not to burn the garlic. Remove the skillet from the heat.

4. Create the Creamy Base: You’ll need a large mixing bowl to combine all the delicious elements. Before adding anything else, lightly whisk the large egg until well beaten. This ensures it integrates smoothly into the sauce.

5. Whisk in the Dairy and Seasonings: To the beaten egg, add the ½ cup of sour cream and ¼ cup of milk, and whisk everything together until thoroughly blended and smooth. Now, it’s time to add the seasonings: the remaining ½ teaspoon of kosher salt, ¼ teaspoon of ground black pepper, and ⅛ teaspoon of ground nutmeg. Incorporate most of the shredded Monterey Jack cheese (reserving about ½ cup for the topping) and 2 tablespoons of the grated Parmesan cheese (reserving the remaining 2 tablespoons for the topping). Mix everything diligently until all the ingredients are well combined and the cheesy mixture is uniform.

6. Combine All Ingredients: Add the cooked spaghetti, the sautéed mushrooms and onions, and the thawed, squeezed-dry spinach to the large mixing bowl with the creamy cheese mixture. Using a large spoon or spatula, stir everything together thoroughly. Make sure to scoop from the bottom of the bowl as you stir, ensuring that all the cheesy goodness, vegetables, and pasta are evenly coated and mixed throughout. This step is key for a consistent flavor in every bite.

7. Prepare for Baking: Transfer the entire spaghetti mixture into the prepared 1 ½ quart casserole or baking dish. Spread it out evenly, ensuring the top is relatively flat.

8. Top and Bake: Sprinkle the reserved ½ cup of Monterey Jack cheese and the remaining 2 tablespoons of grated Parmesan cheese over the top of the spaghetti mixture in the dish. This layer of cheese will become beautifully golden and bubbly during baking. Cover the dish tightly with aluminum foil.

Bake the covered casserole for 25 minutes. After this time, carefully remove the foil cover and continue to bake for another 20 minutes, or until the casserole is bubbling around the edges and the top is a glorious golden brown. For extra assurance, you can check the internal temperature with an instant-read thermometer inserted into the center of the casserole; it should reach 165°F (74°C).

9. Serve and Enjoy: Once baked to perfection, remove the casserole from the oven. You can serve it immediately for a piping hot meal, or for slightly firmer slices and easier handling, allow it to rest for about fifteen minutes before serving. It’s utterly delicious either way! Because this baked spaghetti is a wonderfully rich and satisfying dish on its own, it pairs beautifully with a crisp, light side. Consider serving it alongside a refreshing arugula salad with a zesty vinaigrette or a bright and vibrant citrus salad with mint and honey-lime dressing. These fresh accompaniments will cut through the richness and provide a perfect balance to your meal.

Get Creative: Exciting Recipe Variations for Your Pasta Bake

This baked spaghetti with spinach is incredibly versatile, making it easy to customize according to your taste or what you have on hand. Here are some fantastic variations to inspire your culinary creativity:

• Load Up on More Veggies! Boost the nutritional content and flavor by adding more vegetables. Sauté a finely chopped bell pepper (red or yellow works wonderfully) along with the mushrooms and onions. You could also incorporate diced zucchini, sun-dried tomatoes, or even a handful of chopped kale for extra color and texture.
• Embrace Whole Grains: While traditional spaghetti is delicious, opting for whole wheat pasta adds more fiber and nutrients, making this casserole an even healthier choice. This is especially beneficial if you’re serving the baked spaghetti as a vegetarian main dish. Beyond spaghetti, feel free to experiment with other pasta shapes like rotini, penne, or cavatappi for a different mouthfeel. For gluten-free diners, a high-quality gluten-free pasta can be seamlessly substituted without compromising flavor.
• Experiment with Cheesy Combinations: The beauty of a baked pasta lies in its cheesy core! While Monterey Jack and Parmesan are a fantastic duo, don’t be afraid to try different cheese blends. For an even creamier and richer texture, try adding a layer of cottage cheese or ricotta cheese to the mixture; these also make excellent substitutes for the sour cream, providing a lighter yet still decadent binding element. Shredded mozzarella, fontina, or even a smoky Gouda could introduce exciting new dimensions of flavor.
• Add a Protein Punch: If you’re craving a heartier meal, incorporating meat is simple. Cooked and shredded chicken (our Instant Pot shredded chicken recipe is perfect here), browned ground beef, Italian sausage, or even turkey sausage can be mixed into the pasta along with the vegetables. Be sure to cook any meat thoroughly before adding it to the mixture.
• Spice It Up! For a subtle kick, add a pinch of red pepper flakes to the sautéing vegetables. A blend of Italian herbs (like oregano, basil, and thyme) can also deepen the savory profile.
• No Oven? No Problem! If you’d prefer not to turn on your oven, or simply want a quicker stovetop meal, explore some of our other delicious pasta recipes. Our creamy chicken spinach pasta is a fantastic one-pot wonder, and the Instant Pot lemon pasta with chicken offers speed and convenience without sacrificing flavor.

Beyond the Casserole: Creative Ways to Use Leftover Spaghetti

Never let perfectly good cooked spaghetti go to waste! There are countless ingenious ways to repurpose plain cooked pasta, transforming it into exciting new meals. This baked spaghetti recipe is, of course, a prime example of such culinary alchemy. But the possibilities don’t end there:

• Pizza Baked Pasta: Our super easy pizza baked pasta recipe is another fantastic casserole option, combining the best of pizza flavors with tender pasta.
• Pasta Salads: Chop leftover spaghetti into shorter lengths and toss it into a vibrant summer pasta salad with chicken, fresh vegetables, and a light dressing for a refreshing meal.
• Stir-Fries: Instead of rice or noodles, add your leftover spaghetti to stir-fries. It absorbs flavors beautifully and adds a satisfying texture.
• Soups: Break it into smaller pieces and add it to hearty soups like our creamy chicken enchilada soup with noodles for a comforting and filling addition.

Storage Tips for Plain Cooked Spaghetti: To keep plain cooked spaghetti fresh, refrigerate it promptly in an airtight container for three to five days. For longer storage, freeze it in resealable freezer bags for up to a month. When you’re ready to use it, simply bring a pot of water to a boil, submerge the cooked spaghetti for a minute or two to refresh it, drain, and then serve immediately with your favorite sauce or transform it into another amazing main dish like this baked casserole.

Smart Meal Planning: Make-Ahead Ideas for Baked Spaghetti

Preparing meals ahead of time can be a huge time-saver and stress reducer. This baked spaghetti casserole is an excellent candidate for meal prep:

Get a Head Start: Maximize efficiency by performing these tasks in advance:

• Leftover Pasta: Utilizing leftover cooked pasta is perhaps the biggest time saver for this recipe.
• Pre-Sliced Produce: Purchase already sliced mushrooms from the grocery store, or take a few minutes to prep and slice your own mushrooms and chop your onion and garlic ahead of time. Store them in airtight containers in the refrigerator.
• Thaw Spinach: Thaw your frozen chopped spinach in the refrigerator overnight to ensure it’s ready to go when you are. Don’t forget to squeeze out all excess moisture!

Make the Casserole Ahead: One of the best features of this recipe is its make-ahead potential. The entire casserole can be assembled and then refrigerated or frozen unbaked, giving you a ready-to-bake meal whenever you need it. If you choose to freeze it, ensure it’s in a freezer-safe dish and covered tightly with foil. When you’re ready to bake, remember to thaw the frozen casserole overnight in the refrigerator before baking. Bake it as directed in the recipe, but increase the initial covered baking segment by ten minutes to ensure it heats through evenly. For optimal safety and doneness, check the internal temperature with an instant-read thermometer inserted into the center of the casserole; it should register 165°F (74°C).

Storage & Reheating Tips

Ensuring your leftover baked spaghetti remains delicious and safe to eat is simple with these storage and reheating guidelines:

Refrigerate/Freeze: Any leftover baked pasta bake should be promptly refrigerated within two hours of cooking. Cover it well with plastic wrap or aluminum foil, or transfer it to an airtight container. It will stay fresh in the refrigerator for three to five days. For longer storage, this casserole freezes beautifully. Wrap individual portions or the entire leftover casserole tightly in plastic wrap and then aluminum foil, or place in freezer-safe containers. It can be frozen for up to 3 months, offering a convenient future meal.

Reheat: When you’re ready to enjoy your leftovers, individual portions of baked spaghetti can be easily reheated in the microwave. Place a serving on a microwave-safe plate, cover it loosely, and microwave in 30-second increments, stirring occasionally, until it is heated through to your desired temperature. For a crispier topping reminiscent of its freshly baked state, you can reheat larger portions in the oven at 300°F (150°C) until warmed through, covering with foil initially to prevent drying out and then uncovering for the last few minutes to re-crisp the cheese.

Unlock Your Free Meal Plan!

Are you interested in a thoughtfully curated weekly meal plan that strategically incorporates this delicious baked spaghetti recipe? Look no further! Explore Meal Plan #53. This comprehensive plan provides a wholesome, easy-to-follow recipe for each weekday, complete with a categorized grocery list to streamline your shopping experience. It’s the perfect way to organize your week and enjoy delicious, balanced meals without the daily hassle.

Browse All Meal Plans

Recipe

Baked Spaghetti With Spinach and Mushrooms

4.88 from 8 votes

By Rachel Gurk

Prep Time: 25 minutes mins

Cook Time: 45 minutes mins

Total Time: 1 hour hr 10 minutes mins

Servings: 4

Pin
Print

This rich baked spaghetti with spinach is a delightful vegetarian casserole, boasting a blend of two types of cheese and earthy mushrooms. It’s an incredibly satisfying meal that can be prepared in advance, making it perfect for both weeknight dinners and special occasions.

Ingredients 

• ▢ 8 oz. uncooked spaghetti (see note)
• ▢ 1 tablespoon olive oil
• ▢ 8 oz. sliced fresh mushrooms
• ▢ ½ medium yellow onion, finely chopped
• ▢ ½ teaspoon kosher salt
• ▢ ¼ teaspoon ground black pepper
• ▢ 1 clove garlic, minced
• ▢ 1 large egg, beaten
• ▢ 1 ½ cups shredded Monterey Jack cheese, divided
• ▢ ½ cup sour cream
• ▢ ¼ cup milk
• ▢ 4 tablespoons grated Parmesan cheese, divided
• ▢ ⅛ teaspoon ground nutmeg
• ▢ 1 package (10 oz.) frozen chopped spinach, thawed and moisture squeezed out

Instructions 

• Cook pasta according to package directions until al dente. Drain thoroughly and set aside.
  8 oz. uncooked spaghetti
• Preheat oven to 350°F (175°C) and lightly grease or spray a 1 ½ quart casserole or baking dish with non-stick cooking spray.
• While pasta is cooking, heat 1 tablespoon olive oil in a skillet over medium-high heat. Add mushrooms and onions, sprinkle with ½ teaspoon kosher salt and ¼ teaspoon black pepper. Sauté for 6 to 7 minutes or until mushrooms are golden and onions are soft and translucent. Add minced garlic and cook, stirring, for 1 minute more until fragrant. Remove from heat.
  1 tablespoon olive oil, 8 oz. sliced fresh mushrooms, ½ medium yellow onion, finely chopped, ½ teaspoon kosher salt, ¼ teaspoon ground black pepper, 1 clove garlic, minced
• In a large bowl, whisk the beaten egg. Add ½ cup sour cream, ¼ cup milk, the remaining ½ teaspoon kosher salt, ¼ teaspoon black pepper, and ⅛ teaspoon ground nutmeg. Add 1 cup shredded Monterey Jack cheese and 2 tablespoons grated Parmesan cheese (reserve remaining cheese for topping); mix well. Incorporate the spinach, mushroom mixture, and cooked spaghetti; stir until all ingredients are thoroughly combined and coated.
  1 large egg, beaten, 1 ½ cups shredded Monterey Jack cheese, divided, ½ cup sour cream, ¼ cup milk, 4 tablespoons grated Parmesan cheese, divided, ⅛ teaspoon ground nutmeg, 1 package (10 oz.) frozen chopped spinach, thawed and moisture squeezed out
• Transfer the mixture into the prepared casserole dish. Sprinkle evenly with the remaining ½ cup Monterey Jack cheese and 2 tablespoons Parmesan cheese.
• Bake, covered with aluminum foil, for 25 minutes. Then, remove the cover and continue to bake for another 20 minutes, or until the casserole is bubbling hot and the top is golden brown. For extra assurance, an instant-read thermometer inserted into the center should read 165°F (74°C).

Notes

• Using fresh spinach: If you prefer, you can substitute fresh spinach for frozen. One pound of fresh spinach is equivalent to one 10-ounce package of frozen. Sauté fresh spinach in a skillet until the leaves have wilted, then squeeze out excess moisture.
• Pasta alternatives: Feel free to substitute any type of pasta for spaghetti, including whole wheat varieties, or use leftover cooked pasta you have on hand.
• Make ahead instructions: This casserole can be fully assembled and refrigerated overnight or frozen for later. If frozen, thaw completely in the refrigerator before baking. Bake as directed, adding an additional 10 minutes to the initial covered baking time to ensure it heats through evenly.

Video

Nutrition

Calories: 545kcal, Carbohydrates: 52g, Protein: 27g, Fat: 26g, Saturated Fat: 13g, Polyunsaturated Fat: 2g, Monounsaturated Fat: 9g, Trans Fat: 0.01g, Cholesterol: 107mg, Sodium: 724mg, Potassium: 697mg, Fiber: 5g, Sugar: 6g, Vitamin A: 8952IU, Vitamin C: 7mg, Calcium: 526mg, Iron: 3mg

Nutrition information is automatically calculated, so should only be used as an approximation.

Did You Make This?Share a comment and rating below! I love hearing what you think!