Make a well in the center of mixture.
In another bowl combine milk,egg yolks,melted butter and vanilla.
Pour into well in flour mixture;stir until smooth and creamy.
Preheat waffle iron according to directions.
In another bowl,beat egg whites to soft peaks. Fold one third of egg whites into batter to lighten,then fold in remaining whites. Pour batter onto lightly oiled waffle iron.
Cook according to waffle iron directions. Serve immediately.