2 C. lukewarm milk
Put milk in a large mixing bowl, sprinkle yeast over the top. Stir well to dissolve so no lumps remain. Beat egg yolks and add to cooled yeast mixture. Stir in vanilla & melted butter. Beat the egg whites until stiff; fold into batter. Let stand in a warm place for an hour, or until doubled in size. Use a Belgian waffle iron, fill with about 1 1/2 cups of mixture; cook until golden brown. Serve with syrup or cream and fresh fruit.