Butternut Squash Gratin with Goat Cheese and Hazelnuts

from Bon Appetit
Serves 8

3 1/2 pounds butternut squash (about 2 medium), peeled, seeded, cut into 3/4-inch cubes (8 cups)
2 tablespoons olive oil
Seasalt and black pepper to taste
4 tablespoons (1/2 stick) butter, divided
3 cups sliced leeks (white and pale green parts only)
1 teaspoon sage
1 5.5 oz log soft goat cheese
1 cup heavy whipping cream
1/2 cup hazelnuts, toasted, husked, chopped

1. Preheat oven to 400°F. Place butternut squash cubes and olive oil in large bowl; sprinkle with salt and pepper and toss to coat. Spread out squash cubes on large rimmed baking sheet. Roast until just tender and beginning to brown, stirring occasionally, about 35 minutes.
2. Meanwhile, melt 3 tablespoons butter in heavy medium skillet over medium-low heat. Add sliced leeks and chopped sage; sprinkle with salt and pepper. Sauté until tender but not brown, about 15 minutes.
3. Coat an 11 x 7- inch baking dish with remaining 1 tablespoon butter. Spread half of leek mixture over bottom of prepared baking dish. Sprinkle with half of squash and half of cheese. Repeat layering with leeks, squash, and cheese.  
4. Heat oven to 375°F. Pour cream evenly over gratin. Sprinkle with toasted chopped hazelnuts. Bake uncovered until gratin is heated through and cream is bubbling, about 30 minutes.