Melt the butter in a double boiler and stir in flour until well blended. Slowly add the milk and cook until thick. Add cheese and stir until it melts. Then add the beaten yolks of the eggs and seasonings and cook for 1 minute. Set aside to cool. When cold, add the stiffly beaten egg whites. Mix well and pour into a buttered baking dish. Set dish in pan half filled with hot water and bake at 350-F about 30 minutes. Serve at once. Source: Pennsylvania Dutch Cook Book - Fine Old Recipes, Culinary Arts Press, 1936.