Sprinkle dry yeast over warm milk and stir to dissolve.

Beat egg yolks and add to the yeast mixture along with vanilla.

Sift together flour, salt, and sugar.

Add dry ingredients to wet ingredients.

Stir in melted butter until well combined.

Beat egg whites until stiff peaks form.

Carefully fold the beaten egg whites into the batter.

Let the mixture stand in a warm place for about 45 minutes, or until it doubles in bulk.

Use 1 1/3 cups of batter per waffle in a hot waffle iron.

Cook until golden brown.

Sprinkle with powdered sugar before serving.