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Spaghetti Squash Au Gratin

Spaghetti Squash Au Gratin

Creamy, cheesy, and irresistibly golden on top, this Spaghetti Squash Au Gratin turns tender squash strands into a cozy, lighter twist on classic gratin. It’s simple enough for weeknights yet special enough for holidays and potlucks.
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Prep Time 20 minutes
Cook Time 1 hour
Resting Time 10 minutes
Total Time 1 hour 30 minutes
Course Main Course, Side Dish
Cuisine American
Servings 6 servings
Calories 270 kcal

Equipment

  • Baking Sheet
  • Chef’s knife
  • Large saucepan
  • Whisk
  • 2-quart baking dish
  • Colander

Ingredients
  

Au Gratin Base

  • 1 medium spaghetti squash about 3 lb (1.4 kg)
  • 1 tbsp olive oil
  • 2 tbsp unsalted butter
  • 1/2 cup yellow onion, finely chopped
  • 2 cloves garlic, minced
  • 2 tbsp all-purpose flour
  • 1 1/2 cups milk (whole or 2%)
  • 1 1/2 cups sharp cheddar, shredded
  • 1/2 cup Parmesan cheese, grated
  • 1/2 tsp kosher salt plus more to taste
  • 1/4 tsp black pepper
  • 1/4 tsp ground nutmeg optional

Topping

  • 1/2 cup panko breadcrumbs
  • 1 tbsp unsalted butter, melted
  • 1/4 cup Parmesan cheese, grated
  • 1 tbsp fresh parsley, chopped optional garnish

Instructions
 

  • Preheat oven to 400°F (200°C). Halve the spaghetti squash lengthwise, scoop out the seeds, brush the cut sides with olive oil, and season lightly with salt and pepper. Place cut-side down on a lined baking sheet and roast 35–45 minutes, or until the flesh is tender.
  • When cool enough to handle, use a fork to scrape the flesh into spaghetti-like strands. Transfer to a bowl and let excess moisture drain in a colander (or blot with a clean towel).
  • Make the sauce: In a large saucepan over medium heat, melt the butter. Add the chopped onion and cook until softened, 3–4 minutes. Stir in the garlic for 30 seconds. Whisk in the flour and cook 1 minute. Slowly stream in the milk, whisking constantly, and simmer until thickened and silky, 3–5 minutes.
  • Remove from heat and stir in cheddar and Parmesan until melted. Season with salt, pepper, and nutmeg (if using).
  • Combine the squash strands with the cheese sauce and transfer to a greased 2-quart baking dish, smoothing the top.
  • Mix the topping: toss panko with melted butter and Parmesan, then sprinkle evenly over the casserole.
  • Bake at 400°F (200°C) for 15–20 minutes, until bubbling and golden. For extra color, broil 1–2 minutes, watching closely.
  • Rest 10 minutes before serving. Garnish with parsley and enjoy warm as a side or light main.

Notes

Make-ahead: Roast the squash and prep the sauce up to 2 days in advance; refrigerate separately. Assemble just before baking, adding 5–10 extra minutes if chilled.
Shortcuts: Microwave the whole squash (pierced several times) 5–10 minutes to soften before halving, then finish roasting. Or fully microwave the halves cut-side down in a dish with a splash of water until tender.
Substitutions: Swap cheddar for Gruyère or fontina; use half-and-half for a richer sauce. For a gluten-free topping, try crushed pork rinds or gluten-free panko and replace flour with a 1:1 GF blend or cornstarch slurry.
Leftovers: Store covered in the fridge up to 3–4 days. Reheat in a 350°F (175°C) oven until warmed through to keep the topping crisp, or microwave for a quick reheat.

Nutrition

Calories: 270kcalCarbohydrates: 20gProtein: 12gFat: 16gSaturated Fat: 9gCholesterol: 45mgSodium: 520mgPotassium: 480mgFiber: 3gSugar: 7gVitamin A: 520IUVitamin C: 9mgCalcium: 320mgIron: 1.3mg
Keyword Comfort Food, Spaghetti Squash Au Gratin, Vegetable Casserole
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