1. Preheat Roaster Oven to 400°F.
2. Boil the potatoes in their skins, then refrigerate overnight.
3. Peel the potatoes and grate on a coarse grater into a bowl.
4. Add the cream, onion, salt, pepper, and mix well. Place the mixture in a buttered 9x13-inch casserole dish. Dot the top with the butter.
5. Bake for 1 hour.
Cooked potatoes will grate more easily when cold. Grate the potatoes soon after peeling while they are still cold.
1 tablespoon of dried minced onion can be used in place of a grated 1/2 of a small onion.