1 1/2 tsp. butter
2 1/2 oz. Gruyere cheese, chilled
4 (8 oz.) baking potatoes
1 c. beef stock
1 med. onion, sliced

Preheat oven to 425 degrees. Grease a 13 inch gratin pan with the butter.

Peel and cut the potatoes in half crosswise. Slice. Reserve 1/3 of the cheese. Arrange potatoes and onions in layers. Sprinkle each layer with remaining cheese, salt and pepper to taste. Pour beef stock over the potatoes and top with reserved cheese. Bake until top is deep brown and potatoes are tender, about 50-60 minutes.