3 to 3 1/2 lb. large potatoes, peeled and sliced
2 large onions, sliced
6 tbsp. unsalted butter
1 1/4 c. heavy cream
salt and pepper

Preheat oven to 400°F. Blanch sliced potatoes for 2 minutes; drain well. Place potatoes, onions, butter and cream in a pan. Stir well and cook for about 15 minutes. Transfer to a large, ovenproof dish. Season well and bake for 1 hour, until potatoes are tender.