Creamy Spaghetti Squash Au Gratin

This creamy Spaghetti Squash Au Gratin transforms tender roasted spaghetti squash into a comforting dish baked in a rich cheese sauce with a golden, bubbly topping. It offers a delicious and healthier alternative to traditional mac and cheese that will satisfy your cheesy cravings while sneaking in a serving of vegetables.

I first made this during a chilly weekend when I wanted comfort food without feeling too heavy and it quickly became a family favorite for weeknight dinners and holiday gatherings alike.

Gather Your Ingredients

• One large spaghetti squash: weighing about three to four pounds. Choose one that feels heavy for its size with firm, unblemished skin
• Four tablespoons unsalted butter divided: Butter enriches the cheese sauce and helps sauté aromatics
• One medium yellow onion finely chopped: to add sweetness and depth
• Two cloves garlic minced: for bright savory notes
• Four tablespoons all-purpose flour: which acts as the thickening agent for the sauce
• Three cups whole milk: for creaminess. Whole milk is best to achieve a rich sauce, though you can substitute with a creamy plant-based milk if needed
• Half a teaspoon salt plus more to taste: to enhance savory flavors
• Quarter teaspoon black pepper plus more to season: Freshly ground pepper elevates the dish better than pre-ground
• Quarter teaspoon nutmeg: adds warmth and complexity to the cheese sauce
• One cup grated Gruyere cheese divided: for a nutty melting cheese that forms the flavor base
• One cup grated sharp cheddar cheese divided: which adds tang and sharpness to the blend
• Half a cup grated Parmesan cheese divided: for salty umami richness
• Quarter cup panko breadcrumbs: to create a crunchy golden topping
• Two tablespoons chopped fresh parsley optional: for a fresh garnish that brightens the final dish

How to Make It

Slicing and prepping the squash:

Cut the spaghetti squash lengthwise carefully with a sharp knife. Scoop out the seeds and discard stringy bits for a clean base

Seasoning and roasting the squash:

Brush the cut sides generously with two tablespoons melted butter and sprinkle salt and pepper evenly. Place cut-side down on a parchment-lined baking sheet to roast at four hundred degrees Fahrenheit for forty-five to sixty minutes until tender. The flesh should be easily pierced with a fork

Shredding the squash:

Once the squash is cool enough to handle, use a fork to scrape the flesh into strands resembling spaghetti. Set aside in a bowl

Starting the sauce:

In a large saucepan over medium heat, melt the remaining two tablespoons of butter.

Cooking the aromatics:

Add the chopped onion and cook slowly for five to seven minutes until softened and translucent, developing sweetness. Then stir in minced garlic and cook an additional minute until fragrant

Making the roux:

Sprinkle the flour over the buttered onion and garlic mixture, stirring constantly for one to two minutes to cook out the raw flour taste and create a smooth roux

Adding and thickening the milk:

Slowly whisk in the milk a little at a time to avoid lumps. Continue whisking until smooth

Simmering the sauce:

Bring the sauce to a gentle simmer over medium heat and stir continuously. Lower the heat and maintain a gentle simmer for five to seven minutes until slightly thickened

Seasoning the sauce:

Add salt, pepper, and a pinch of nutmeg. Taste and adjust the flavors to your preference

Incorporating the cheese:

Remove the sauce from heat and stir in three quarters of the Gruyere, cheddar, and Parmesan cheeses until melted into a creamy sauce. Reserve the remaining cheese for the topping

Combining sauce and squash:

Fold the shredded spaghetti squash gently into the cheese sauce to coat evenly without crushing the strands

Transferring and topping:

Pour the mixture into a greased nine by thirteen inch baking dish. In a small bowl combine the reserved Gruyere, cheddar, Parmesan, and panko breadcrumbs. Sprinkle this topping evenly over the casserole

Baking the casserole:

Place in the preheated oven and bake for twenty to twenty-five minutes until the topping is bubbly and beautifully browned

Resting and serving:

Let the au gratin rest for five to ten minutes to set before serving. Garnish with chopped fresh parsley if desired and enjoy hot

One of my favorite things about this recipe is the Gruyere cheese which melts into a silky sauce with an almost caramel-like nuttiness. I remember the first time my mom made this recipe for a potluck and everyone kept asking for seconds. The crunch from the panko topping combined with creamy strands of squash is pure comfort in every bite.

Flavor Boosters

Adding fresh herbs such as chopped parsley brightens up the dish, while a dash of freshly ground black pepper enhances the cheesy flavors without overpowering them.

Serving Suggestions

This dish pairs wonderfully with a crisp green salad to balance richness. Add roasted or sautéed vegetables on the side like green beans or Brussels sprouts for a complete meal. Leftover au gratin also works well as a filling for baked omelets or a topping on toasted crusty bread for quick snacks.

Creative Twists

Try adding cooked bacon or sausage for a meatier meal without losing the classic creamy feel. You can also swap Gruyere with fontina or mozzarella for a milder melt, or replace panko with crushed crackers or regular breadcrumbs for a different topping texture.

I learned the hard way to roast the spaghetti squash cut-side down to keep it moist and tender rather than drying out the flesh during baking.

Recipe FAQs

→ How do I prepare the spaghetti squash for this dish?

Cut the squash in half lengthwise, scoop out seeds, then roast cut-side down until tender. After cooling, shred the flesh into strands with a fork.

→ What cheeses are used in the creamy sauce?

The sauce combines Gruyere, sharp cheddar, and Parmesan cheeses for a rich, layered flavor.

→ Can I make this dish ahead of time?

Yes, assemble the dish and refrigerate for up to 24 hours. Add extra baking time if baking from cold.

→ What gives the topping its golden, bubbly texture?

A mixture of cheeses and panko breadcrumbs creates a crunchy, golden crust when baked.

→ Are there seasoning tips to enhance the flavor?

Season the sauce with salt, pepper, and a pinch of nutmeg. For a kick, add red pepper flakes to the cheese sauce.