• Preheat the oven to 375°F.
• Prepare the squash: Cut the butternut squash in half, scoop out the seeds, peel, and slice thinly into half-moons using a mandolin or sharp knife.
  20 ounces butternut squash
• Mix the cream: In a bowl, whisk together the heavy cream, salt, black pepper, nutmeg, and garlic powder.
  1 cup heavy cream, ½ teaspoon salt, ¼ teaspoon nutmeg, ¼ teaspoon black pepper, ½ teaspoon garlic powder
• Grease the pan: Lightly grease a 2-quart baking dish with butter or olive oil.
  1 tablespoon olive oil
• Layer the squash: Arrange half of the squash slices in the bottom of the dish. I like to use irregular pieces on the bottom and save the more uniform slices for the top.
• Add the cream and cheese: Pour ⅓ of the cream mixture over the squash and sprinkle with grated cheese.
  1 ¼ cup Gruyère cheese
• Repeat the layers: Add the remaining squash slices, tucking sage leaves between some of the layers. Pour over the rest of the cream mixture and top with the remaining grated cheese.
  5 sage leaves or thyme sprigs
• Bake covered: Cover the dish with foil and bake for 45 minutes.
• Bake uncovered: Remove the foil and bake for another 15 minutes, or until the top is golden brown and bubbly.

For a crispy sage topping (optional):

• Melt butter: In a skillet over medium heat, melt 1 tablespoon of butter.
• Crisp the sage: Add 4-5 sage leaves and cook for about 30 seconds per side until crisp.
• Drain: Transfer to a paper towel to absorb excess oil, then sprinkle over the casserole before serving.