Spaghetti Squash Au Gratin

This Spaghetti Squash Au Gratin is a comforting yet lighter twist on traditional au gratin dishes that makes for a perfect cozy dinner or side during cooler months. It uses the natural texture of spaghetti squash combined with a creamy, cheesy sauce to create a satisfying meal with a bit of indulgence but less heaviness. It is a great way to enjoy vegetables in a crowd-pleasing format that feels special but is easy enough for weeknights.

I first made this on a whim when wanting comfort food without turning to potatoes or pasta and it quickly became a family favorite, especially for holiday dinners as a side.

Ingredients

• Large spaghetti squash: about 3 to 4 pounds Choose a firm, heavy squash with no soft spots for best texture when shredded
• Unsalted butter divided: Butter adds richness and helps develop the flavor base in the sauce
• Medium yellow onion finely chopped: Onions bring sweetness and savoriness that complements the cheese
• Garlic cloves minced: Fresh garlic brightens the sauce and layers additional flavor
• All-purpose flour: This will help thicken the sauce creating the creamy texture essential for au gratin dishes
• Whole milk: Use full fat milk for richness, which blends smoothly into the roux for that silky sauce
• Salt and black pepper: These seasonings balance and enhance the overall flavor of the gratin
• Nutmeg: Adds a gentle warmth and complexity that lifts the creamy cheese sauce
• Gruyere cheese grated: This cheese melts beautifully and brings a nutty depth to the dish
• Sharp cheddar cheese grated: Sharp cheddar adds a familiar cheesy tang and sharpness to cut through the creaminess
• Parmesan cheese grated: Parmesan introduces an umami saltiness and helps with browning the crust
• Panko breadcrumbs: These create a crisp, golden topping that contrasts the creamy interior
• Fresh parsley chopped for garnish(optional): Parsley adds a fresh herbal lift and brightens the plate when served

Instructions

Build The Base:

Preheat your oven to 400 degrees Fahrenheit. Then cut the spaghetti squash in half lengthwise and scoop out the seeds and stringy bits. Drizzle the cut sides with two tablespoons of melted butter and sprinkle generously with salt and pepper. This seasoning on the squash surface will enhance flavor during roasting.

Roast The Squash:

Place the squash halves cut-side down on a parchment-lined baking sheet. Roast for 45 to 60 minutes until the flesh is tender and easily pierced with a fork. The slow roasting softens the squash and allows it to develop subtle caramelized flavors.

Prepare The Sauce:

While the squash cools, melt the remaining two tablespoons of butter in a large saucepan over medium heat. Add the finely chopped onions and cook for about five to seven minutes until they become translucent and soft. Add the minced garlic and cook for another minute until fragrant. This step builds the savory aromatic base.

Make The Roux And Sauce:

Sprinkle the flour evenly over the onion and garlic mixture then stir constantly for one to two minutes to cook out the raw flour taste. Gradually whisk in the milk a little at a time ensuring no lumps form. Bring the sauce to a simmer over medium heat while stirring constantly. Reduce the heat and let it gently simmer for five to seven minutes until thickened to a creamy consistency.

Season And Add Cheese:

Stir in salt, pepper, and nutmeg then taste and adjust seasoning as needed. Remove from heat and add three quarters of the Gruyere cheese, cheddar cheese, and Parmesan cheese. Stir until all the cheese melts smoothly creating a rich sauce.

Combine Squash And Sauce:

Using a fork, shred the cooled squash flesh into spaghetti-like strands. Gently fold these strands into the cheese sauce. Pour this mixture evenly into a greased nine by thirteen inch baking dish shaping it smoothly.

Prepare Topping And Bake:

In a small bowl, mix the remaining cheeses with panko breadcrumbs. Sprinkle this mixture evenly over the top of the squash. Bake for twenty to twenty-five minutes until the topping is golden brown and bubbly.

Rest And Serve:

Remove from oven and allow to rest five to ten minutes so the gratin can set slightly. Garnish with chopped fresh parsley if desired and serve hot.

I love how the Gruyere adds a nutty, almost buttery note that makes this dish feel elevated without fuss. One holiday, my family kept asking for seconds and it was the first time a vegetable dish outshined the star mains, making it an instant classic at our table.

Storage Tips

This gratin stores well wrapped in the fridge for up to four days. Reheat uncovered in a moderate oven to keep topping crisp. Avoid microwaving for best texture.

Ingredient Swaps

You can substitute whole milk with half and half for a richer sauce or a nut milk like cashew for dairy free. Try mozzarella instead of Gruyere and sharp white cheddar if you prefer less intense cheese flavors. For topping, crushed cornflakes work in place of panko breadcrumbs.

Serving Ideas

Pair this gratin with roasted chicken or pork for a comforting dinner. It’s also excellent alongside a simple green salad dressed with lemon vinaigrette to cut richness. Leftover scallions sprinkled on top make a fresh garnish variation.

This dish balances comfort with a lighter feel, making it perfect for cozy nights and holiday tables alike.

Frequently Asked Recipe Questions

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

Cut the squash in half, remove seeds, drizzle with butter, season, and roast cut-side down until tender. Once cooled, shred with a fork into strands.

→ What cheeses are ideal for the au gratin sauce?

Gruyere, sharp cheddar, and Parmesan blend well to create a rich, smooth, and flavorful cheese sauce that complements the squash.

→ How is the sauce thickened and kept creamy?

A roux made from butter and flour is cooked before gradually whisking in milk, then simmered to thicken before adding the cheeses.

→ Can I use a different breadcrumb for the topping?

Panko breadcrumbs provide a light, crispy topping, but you can substitute regular breadcrumbs if preferred for a denser crust.

→ What seasonings enhance the flavor of this dish?

Salt, black pepper, and a pinch of nutmeg add balance and depth to the creamy cheese sauce and roasted squash.

→ How long should the dish rest before serving?

Allow it to rest for 5-10 minutes after baking to let the sauce set slightly, making it easier to serve.