Butternut Squash Au Gratin is a decadent side dish that is so perfect for a holiday meal or special occasion! Bubbly parmesan cheese, fresh sage, and sauteed leeks ties this dish together so well.
Preheat the oven to 400 degrees F. Prepare the butternut squash by peeling, removing the seeds, and dicing into cubes. Lightly toss with oil, sprinkle with salt, and assemble across a large sheet pan. Transfer to the oven and roast for about 25 - 30 minutes, or until softened.
Meanwhile, heat a large saute pan to medium heat. Add the butter, sliced leeks, garlic, and sage. Saute until softened and golden brown, stirring occasionally. This should take 10-12 minutes. Set aside.
Once the butternut squash is ready, remove from oven. Prepare a smaller casserole dish (9x9, 8x11). Layer the dish as follows: start with half of the leek mixture, then arrange half of the butternut squash on top. Add another layer of leeks, and top with another layer of butternut squash. Pour the cream on top, then sprinkle with parmesan cheese.
Bake uncovered at 375 F for 27-30 minutes, or until bubbly and golden. Remove from heat. Sprinkle with salt and pepper to taste.