Cut your onion in half, then into slices. Over a medium-low heat carmelize the onion in butter for about 10 minutes.
In a buttered baking dish layer cream, potatoes, salt,pepper, cheese, and onions. She did about 3 layers and in each layer grate a little bit of fresh nutmeg. Finish your final layer with cheese and several small dobs of butter. Pour any leftover milk and cream around the edge of the baking dish.
Cover with foil and bake at 350º for 30 minutes. Cook uncovered for an additional 30 minutes.