2 1/2 lbs. potatoes, peeled and sliced
4 tbsp. butter
1 1/4 c. gruyere or Swiss cheese
Salt
Pepper
1 c. beef stock
1 egg
1/2 c. sour cream
1/2 c. whipping cream

Drop potatoes into cold water and bring to a boil and cook for 10 minutes. Drain potatoes and dry on large towel. In a casserole, arrange layers of potatoes, dotting each layer with butter and sprinkling lightly with salt and pepper and cheese. Repeat layers, ending with cheese, reserving 3 tablespoons.

Bring beef stock almost to boil and gently pour over potatoes. Bake for 45 minutes. Beat egg into both creams, add 3 tablespoons cheese and spread over casserole. Return to oven until golden, about 5 minutes. Garnish and serve.