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Spaghetti Squash Au Gratin – Easy Creamy Casserole

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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
  • 1large spaghetti squash (about3–4pounds)
  • 4 tablespoonsunsalted butter, divided
  • 1medium yellow onion, finely chopped
  • 2cloves garlic, minced
  • 4 tablespoonsall-purpose flour (or almond flour for gluten-free)
  • 3 cupswhole milk
  • 1/2 teaspoonsalt, plus more to taste
  • 1/4 teaspoonblack pepper
  • 1/4 teaspoonnutmeg
  • 1 cupgrated Gruyere cheese, divided
  • 1 cupgrated sharp cheddar cheese, divided
  • 1/2 cupgrated Parmesan cheese, divided
  • 1/4 cuppanko breadcrumbs (or crushed pork rinds for keto)
  • 2 tablespoonschopped 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.

Nutrition

Find it online: https://www.delicetreats.com/spaghetti-squash-au-gratin-easy-casserole/