Sweet Potato Gratin

3 tablespoons butter

4 pounds sweet potatoes, peeled and cut crosswise into 1/4-in.-thick slices

3/4 cup grated parmesan cheese

2 cups heavy whipping cream

1 teaspoon salt

1/2 teaspoon freshly ground black pepper

1/4 teaspoon cayenne

1. Preheat oven to 400°. Butter a 9- by 13-in. baking dish with 1 tbsp. butter. Arrange a third of the sweet potatoes, overlapping slightly, in the dish. Sprinkle with 1/4 cup cheese. Repeat with two more layers of sweet potatoes and cheese.

2. In a small bowl, combine cream, salt, pepper, and cayenne. Pour over potatoes. Dot with the remaining 2 tbsp. butter. Cover dish with foil and bake 20 minutes. Remove foil and continue baking until sweet potatoes are tender and top is browned, 20 to 25 minutes.