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Spaghetti Squash Au Gratin Recipe

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★★★★★

4.9 from 116 reviews

Spaghetti Squash Au Gratin is a delicious and healthy twist on the classic au gratin dish, featuring tender roasted spaghetti squash tossed in a creamy cheese sauce made with Gruyere, sharp cheddar, and Parmesan, topped with a golden breadcrumb crust. This comforting casserole is perfect as a nutritious side or a satisfying vegetarian main course.

Ingredients

Scale

Spaghetti Squash

  • 1 large spaghetti squash (about 3–4 pounds)
  • 2 tablespoons unsalted butter, melted (for squash)
  • Salt and pepper, to taste

Creamy Cheese Sauce

  • 2 tablespoons unsalted butter
  • 1 medium yellow onion, finely chopped
  • 2 cloves garlic, minced
  • 4 tablespoons all-purpose flour
  • 3 cups whole milk
  • 1/2 teaspoon salt
  • 1/4 teaspoon black pepper
  • 1/4 teaspoon nutmeg
  • 3/4 cup grated Gruyere cheese
  • 3/4 cup grated sharp cheddar cheese
  • 1/4 cup grated Parmesan cheese

Topping

  • 1/4 cup grated Gruyere cheese
  • 1/4 cup grated sharp cheddar cheese
  • 1/4 cup grated Parmesan cheese
  • 1/4 cup panko breadcrumbs

Garnish (optional)

  • 2 tablespoons chopped fresh parsley

Instructions

  1. Preheat the Oven: Preheat your oven to 400°F (200°C) to prepare for roasting the spaghetti squash.
  2. Prepare the Squash: Cut the spaghetti squash in half lengthwise and scoop out the seeds and stringy bits to create hollow halves.
  3. Season the Squash: Drizzle the cut sides of each squash half with 2 tablespoons of melted butter, then sprinkle generously with salt and pepper to enhance flavor during roasting.
  4. Roast the Squash: Place the squash halves cut-side down on a parchment-lined baking sheet. Roast for 45-60 minutes or until the flesh is tender and easily pierced by a fork.
  5. Shred the Squash: Once cooled enough to handle, use a fork to scrape the flesh into spaghetti-like strands. Set this aside for the sauce mixture.
  6. Melt Butter: In a large saucepan over medium heat, melt the remaining 2 tablespoons of butter to prepare the base of the cheese sauce.
  7. Sauté Onion and Garlic: Add the finely chopped onion to the melted butter and cook until softened and translucent, about 5-7 minutes. Add the minced garlic and sauté for an additional minute until fragrant.
  8. Make a Roux: Sprinkle the all-purpose flour over the onion and garlic mixture. Cook, stirring constantly, for 1-2 minutes to form a roux that will thicken the sauce.
  9. Whisk in Milk: Gradually add the whole milk to the roux, whisking continuously to prevent lumps and create a smooth sauce.
  10. Simmer the Sauce: Bring the sauce to a gentle simmer over medium heat. Stir constantly, then reduce the heat to low and continue to simmer for 5-7 minutes until slightly thickened.
  11. Season the Sauce: Stir in salt, black pepper, and nutmeg. Taste and adjust seasonings as needed to ensure balanced flavor.
  12. Add Cheese: Remove the saucepan from heat and stir in 3/4 cup each of Gruyere and cheddar cheeses and 1/4 cup Parmesan until fully melted and the sauce is smooth and creamy. Reserve the remaining cheeses for topping.
  13. Combine Squash and Sauce: Gently fold the shredded spaghetti squash into the cheese sauce, ensuring even coating without breaking the strands too much.
  14. Transfer to Baking Dish: Pour the cheesy spaghetti squash mixture into a greased 9×13 inch baking dish, spreading evenly.
  15. Prepare the Topping: In a small bowl, mix remaining 1/4 cup each of Gruyere, cheddar, Parmesan cheeses, and 1/4 cup panko breadcrumbs to create a crunchy cheesy crust.
  16. Sprinkle the Topping: Evenly distribute the breadcrumb and cheese mixture over the top of the casserole.
  17. Bake Au Gratin: Bake in the preheated oven for 20-25 minutes until the topping is golden brown and bubbling, indicating the cheese is melted and crispy.
  18. Rest Before Serving: Remove from oven and let the dish rest for 5-10 minutes to set and cool slightly for easier serving.
  19. Garnish and Serve: Optionally sprinkle chopped fresh parsley over the top for a fresh finish. Serve hot and enjoy your creamy, cheesy spaghetti squash au gratin!

Notes

  • You can substitute whole milk with 2% milk or a lactose-free alternative if desired, but whole milk gives the best creamy texture.
  • Use freshly grated cheeses for the best melting and flavor results.
  • If you prefer a spicier version, add a pinch of cayenne pepper or smoked paprika to the cheese sauce.
  • Panko breadcrumbs provide a light, crispy topping, but you can use regular breadcrumbs if needed.
  • Make sure to cool the roasted squash enough before shredding and mixing with the sauce to avoid curdling or splitting the cheese sauce.
  • This dish can be made ahead and reheated; cover with foil and bake at 350°F (175°C) until warmed through.

Keywords: spaghetti squash, au gratin, healthy casserole, cheese sauce, roasted vegetables, vegetarian side dish

Find it online: https://platedbyemma.com/spaghetti-squash-au-gratin-recipe/