Pam's Boiled Custard

Put milk in a double boiler (or if you don't have one, set your pan in a skillet of water). Mix together sugar and flour and slowly stir into milk. Add egg yolks (be sure you do this before the milk gets too hot so your eggs don't cook too fast). Stir until milk comes to a boil. Continue stirring until the mixture thickens. Remove from heat. Add vanilla." Allow to cool slightly. Beat egg whites and fold in. Serve in a pitcher.