Sarah's very favorite holiday recipe--Sweet Potato Gratin

from the kitchen of Renata Riley (my great aunt)
Serves 8 (this can be halved for a smaller crowd)

Ingredients
3 TBSP butter
4 lbs sweet potatoes, peeled & cut into ¾ in thick slices
¾ cup grated Parmesan cheese
2 cups heavy whipping cream
1 tsp salt
¼ tsp freshly ground black pepper
¼ tsp cayenne pepper

Directions
Preheat oven to 400.
Butter a 9x13 inch baking dish w/ 1 tbsp butter.
Arrange a third of the sweet potatoes, overlapping slightly in the dish.
Sprinkle w/ ¼ cup cheese.
Repeat with two more layers of sweet potatoes and cheese.
In small bowl combine cream, salt, pepper & cayenne. Pour over potatoes. Dot with the remaining 2 tbsp butter.
Cover dish w/ foil & bake 20 min.
Remove foil & continue baking until sweet potatoes are tender & top is browned—20-25 minutes.