Put the butter in the frying pan, and as it melts add the flour, and let it blend, rubbing smooth, without browning. Then add the Consomme or water and the cream, and stir constantly till the mixture boils. Then take the saucepan from the fire, and add the cheese, well grated, and the well-beaten yolks of the eggs. Salt and pepper to taste. Beat all thoroughly till light. Mash the Potatoes well, and place, first, a layer of the sauce in the saucepan, and then the Potatoes, and so on till the sauce forms the top layer. Sprinkle this lightly with bread crumbs, and set in the oven and let bake ten minutes. When it comes to a nice brown, serve in the dish in which it was baked.