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Single serving of spaghetti squash au gratin garnished with fresh herbs

Spaghetti Squash Au Gratin – Easy Creamy Casserole


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  • Author: Patricia Jannet
  • Total Time: 1 hour 20 minutes
  • Yield: 6 servings 1x
  • Diet: Vegetarian

Description

Spaghetti Squash Au Gratin is a creamy, cheesy, low-carb comfort food made with roasted squash, a rich homemade cheese sauce, and a golden crispy topping. It’s a delicious and healthier alternative to traditional potato gratins.


Ingredients

Scale
  • 1 large spaghetti squash (about 34 pounds)
  • 4 tablespoons unsalted butter, divided
  • 1 medium yellow onion, finely chopped
  • 2 cloves garlic, minced
  • 4 tablespoons all-purpose flour (or almond flour for gluten-free)
  • 3 cups whole milk
  • 1/2 teaspoon salt, plus more to taste
  • 1/4 teaspoon black pepper
  • 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 (or crushed pork rinds for keto)
  • 2 tablespoons chopped fresh parsley (optional)

Instructions

  1. Preheat oven to 400°F (200°C).
  2. Cut spaghetti squash in half lengthwise and scoop out seeds.
  3. Brush cut sides with 2 tablespoons melted butter, season with salt and pepper.
  4. Place cut-side down on parchment-lined baking sheet and roast for 45–60 minutes until fork-tender.
  5. Let squash cool, then shred flesh into strands with a fork and set aside.
  6. In a saucepan, melt remaining 2 tablespoons butter over medium heat.
  7. Sauté onion until translucent (5–7 minutes), then add garlic and cook 1 more minute.
  8. Stir in flour and cook for 2 minutes, forming a roux.
  9. Gradually whisk in milk until smooth; simmer for 5–7 minutes until thickened.
  10. Stir in salt, pepper, and nutmeg. Remove from heat.
  11. Add 3/4 cup Gruyere, 3/4 cup cheddar, and 1/4 cup Parmesan. Stir until melted.
  12. Combine shredded squash with cheese sauce and mix gently.
  13. Transfer to greased 9×13-inch baking dish.
  14. Mix remaining cheeses and breadcrumbs; sprinkle over top.
  15. Bake for 20–25 minutes until top is golden and bubbly.
  16. Let rest 5–10 minutes before serving. Garnish with parsley if desired.

Notes

  • Use quality cheese for best flavor.
  • Do not over-roast the squash to avoid a mushy texture.
  • Make ahead: assemble up to 24 hours in advance and bake when ready.
  • Add red pepper flakes for spice.
  • Gluten-free option: use almond flour and gluten-free breadcrumbs.
  • Add protein like bacon, ham, or chicken for a heartier dish.
  • Prep Time: 20 minutes
  • Cook Time: 60 minutes
  • Category: Side Dish
  • Method: Bake
  • Cuisine: American

Nutrition

  • Serving Size: 1 portion (approx. 1/6 of dish)
  • Calories: 390
  • Sugar: 8g
  • Sodium: 600mg
  • Fat: 25g
  • Saturated Fat: 15g
  • Unsaturated Fat: 9g
  • Trans Fat: 0g
  • Carbohydrates: 22g
  • Fiber: 6g
  • Protein: 18g
  • Cholesterol: 90mg