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Sage Butternut Squash Gratin

A creamy, savory, and elegant casserole with layers of thinly sliced butternut squash, sage-infused cream, and a crispy Gruyère cheese topping.
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Prep Time 30 minutes
Cook Time 1 hour 5 minutes
Total Time 1 hour 35 minutes
Servings: 6 servings
Course: Main Course, Side Dish
Cuisine: American, French
Calories: 385

Ingredients
  

Main Components
  • 1 large butternut squash about 3-4 lbs, peeled, seeded, thinly sliced
  • 2 tbsp unsalted butter for sautéing and greasing
  • 1 large shallot finely minced
  • 3 cloves garlic minced
  • 2 tbsp fresh sage leaves finely chopped
  • 1 cup heavy cream
  • 1 cup whole milk
  • 1 tsp kosher salt
  • 0.5 tsp black pepper freshly ground
  • 0.25 tsp nutmeg freshly grated
Cheese Topping
  • 1.5 cups Gruyère cheese grated, divided
  • 0.5 cup Parmesan cheese grated
  • 0.33 cup panko breadcrumbs
Garnish
  • 6 leaves fresh sage whole, for frying

Equipment

  • 9x9 inch or 2-quart baking dish
  • Mandoline or sharp chef's knife
  • Medium Saucepan
  • Box Grater

Method
 

  1. Preheat oven to 375°F (190°C). Generously butter a 2-quart baking dish.
  2. In a saucepan, melt butter over medium heat. Add shallot; cook until soft (4-5 mins). Add garlic and chopped sage; cook 1 minute until fragrant.
  3. Pour in cream and milk. Add salt, pepper, and nutmeg. Heat until just simmering. Remove from heat. Stir in 1 cup Gruyère and all Parmesan until melted and smooth.
  4. Arrange a layer of sliced squash in the prepared dish. Pour over a third of the cream sauce. Repeat layers, ending with sauce.
  5. Combine remaining 1/2 cup Gruyère with panko. Sprinkle evenly over the gratin.
  6. Cover with foil and bake for 30 minutes. Remove foil and bake for 25-35 more minutes, until squash is tender, sauce is bubbly, and top is golden brown.
  7. While baking, fry whole sage leaves in butter until crisp. Let gratin rest for 15 minutes before serving. Garnish with fried sage.

Notes

Letting the gratin rest after baking is crucial for the sauce to set. For best results, use a mandoline for uniformly thin squash slices. Can be assembled a day ahead and refrigerated before baking.