Introduction

Spaghetti Squash Au Gratin is a creamy, cheesy twist on the classic vegetable side dish. Roasted spaghetti squash strands are combined with a rich cheese sauce and baked until golden and bubbly. It’s a comforting, flavorful way to enjoy this nutritious squash.

A square piece of baked macaroni and cheese sits on a clean white plate, showing three visible layers: at the bottom, a dense creamy layer of tender macaroni pasta in pale yellow; the middle is a smooth, slightly melted cheese layer in light golden yellow; and the top layer is a crispy, golden brown crust with some dark brown toasted spots, textured and bubbling, garnished with a small sprig of fresh green thyme in the center. The plate is set on a white marbled surface with a blurred white cloth and silver fork in the background. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

1 large spaghetti squash (about 3-4 pounds)
4 tablespoons unsalted butter, divided
1 medium yellow onion, finely chopped
2 cloves garlic, minced
4 tablespoons all-purpose flour
3 cups whole milk
1/2 teaspoon salt, plus more to taste
1/4 teaspoon black pepper, plus more to taste
1/4 teaspoon nutmeg
1 cup grated Gruyere cheese, divided
1 cup grated sharp cheddar cheese, divided
1/2 cup grated Parmesan cheese, divided
1/4 cup panko breadcrumbs
2 tablespoons chopped fresh parsley, for garnish (optional)

Instructions

Step 1: Preheat oven to 400°F (200°C).
Step 2: Cut the spaghetti squash in half lengthwise. Scoop out the seeds and stringy bits.
Step 3: Drizzle the cut sides of the squash with 2 tablespoons of melted butter. Sprinkle generously with salt and pepper.
Step 4: Place the squash halves cut-side down on a baking sheet lined with parchment paper. Roast for 45-60 minutes, or until the squash is easily pierced with a fork and the flesh is tender.
Step 5: Once cool enough to handle, use a fork to shred the flesh into spaghetti-like strands. Set aside.
Step 6: In a large saucepan over medium heat, melt the remaining 2 tablespoons of butter.
Step 7: Add the chopped onion to the melted butter and cook until softened and translucent, about 5-7 minutes. Add the minced garlic and cook for another minute, until fragrant.
Step 8: Sprinkle the flour over the onion and garlic mixture. Cook, stirring constantly, for 1-2 minutes to create a roux.
Step 9: Gradually whisk in the milk, a little at a time, ensuring that there are no lumps. Continue whisking until the sauce is smooth.
Step 10: Bring the sauce to a simmer over medium heat, stirring constantly. Reduce the heat to low and simmer for 5-7 minutes, or until the sauce has thickened slightly.
Step 11: Stir in the salt, pepper, and nutmeg. Taste and adjust seasonings as needed.
Step 12: Remove the saucepan from the heat. Stir in 3/4 cup of the Gruyere cheese, 3/4 cup of the cheddar cheese, and 1/4 cup of the Parmesan cheese until melted and smooth. Reserve the remaining cheese for topping.
Step 13: Add the shredded spaghetti squash to the cheese sauce and stir gently to combine.
Step 14: Pour the spaghetti squash mixture into a greased 9×13 inch baking dish.
Step 15: In a small bowl, combine the remaining 1/4 cup Gruyere, 1/4 cup cheddar, 1/4 cup Parmesan, and panko breadcrumbs.
Step 16: Sprinkle the cheese and breadcrumb mixture evenly over the top of the squash.
Step 17: Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and bubbly.
Step 18: Remove from the oven and let rest for 5-10 minutes before serving.
Step 19: Garnish with chopped fresh parsley if desired. Serve hot and enjoy!

Tips & Variations

For a richer flavor, use half-and-half instead of whole milk for the sauce.
Try adding cooked bacon or sautéed mushrooms to the cheese sauce for extra depth.
Panko breadcrumbs help create a crunchy topping, but you can substitute with crushed crackers or omit them for a gluten-free version.
Use a mixture of cheeses you have on hand if Gruyere or sharp cheddar isn’t available; mozzarella or fontina work well too.

Storage

Store leftover Spaghetti Squash Au Gratin in an airtight container in the refrigerator for up to 3 days. Reheat gently in the oven at 350°F (175°C) until warmed through to preserve the crispy topping, or microwave individual portions if short on time.

How to Serve

A square piece of baked macaroni and cheese sits on a white plate, showing three visible layers of soft, creamy pasta beneath a golden-brown, crispy top layer with darker toasted spots. The macaroni noodles are tightly packed and have a pale yellow cheese sauce that looks smooth and gooey. On top of the crispy crust, there is a small green sprig of herb, adding a fresh touch. The plate is placed on a white marbled texture, with part of a beige cloth and a fork visible in the blurred background. Photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I use frozen spaghetti squash for this recipe?

Fresh spaghetti squash provides the best texture and flavor, but you can use frozen cooked spaghetti squash if needed. Thaw and drain well before combining with the sauce.

How do I know when the sauce has thickened enough?

The sauce should coat the back of a spoon and have a creamy consistency that clings well to the squash strands. If it’s too thin, continue simmering a few minutes longer.