Ingredients
Scale
- 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
- Preheat oven to 400u00b0F (200u00b0C).
- Prepare the squash: Cut the spaghetti squash in half lengthwise. Scoop out the seeds and stringy bits.
- Season the squash: Drizzle the cut sides of the squash with 2 tablespoons of melted butter. Sprinkle generously with salt and pepper.
- Roast the squash: 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.
- Shred the spaghetti squash: Once cool enough to handle, use a fork to shred the flesh into spaghetti-like strands. Set aside.
- Melt the butter: In a large saucepan over medium heat, melt the remaining 2 tablespoons of butter.
- Sautu00e9 the onion and garlic: 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.
- Make a roux: Sprinkle the flour over the onion and garlic mixture. Cook, stirring constantly, for 1-2 minutes to create a roux.
- Whisk in the milk: Gradually whisk in the milk, a little at a time, ensuring that there are no lumps. Continue whisking until the sauce is smooth.
- Simmer the sauce: 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.
- Season the sauce: Stir in the salt, pepper, and nutmeg. Taste and adjust seasonings as needed.
- Add the cheese: 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 the cheese is melted and the sauce is smooth and creamy. Reserve the remaining cheese for topping.
- Combine squash and sauce: Add the shredded spaghetti squash to the cheese sauce and stir gently to combine.
- Transfer to baking dish: Pour the spaghetti squash mixture into a greased 9×13 inch baking dish.
- Prepare the topping: In a small bowl, combine the remaining 1/4 cup Gruyere cheese, 1/4 cup cheddar cheese, 1/4 cup Parmesan cheese, and panko breadcrumbs.
- Sprinkle the topping: Sprinkle the cheese and breadcrumb mixture evenly over the top of the spaghetti squash.
- Bake the au gratin: Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and bubbly.
- Let it rest: Remove the au gratin from the oven and let it rest for 5-10 minutes before serving.
- Garnish and serve: Garnish with chopped fresh parsley, if desired. Serve hot and enjoy!