In a small bowl, dissolve the yeast in 1 cup of the lukewarm milk. In large deep mixing bowl (the dough will double or triple in volume), whisk the egg yolks with 1/2 cup of the remaining milk and the melted butter and margarine. Add the yeast mixture, sugar and salt. Gradually add the flour to the batter by sifting it in. Alternate additions of flour with the remaining 4 1/2 cups milk. Stir with a wooden spoon after each addition. Fold in the beaten egg whites. Cover with a clean towel and put in a warm place. Let rise for 1 hour. The batter should double or even triple in volume. Check the batter from time to time to make sure it isn't about to erupt. Stir it down once or twice. Bake the waffles in a hot waffle iron. The easiest way to get the batter onto the waffle iron is to transfer the batter into a water pitcher and pour the batter from the pitcher. Serve the baked waffles with confectioners' sugar and butter, or whipped cream and fresh fruit. Allow any leftover waffles to cool on a rack before storing.
Place sugar and vanilla bean in food processor fitted with a metal blade. Process until the vanilla bean is finely minced. Strain sugar through a sieve to remove any large pieces of vanilla bean. Store in an airtight container. It will keep indefinitely.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.