Good-Cooking - Belgian Waffles

Ingredients

• 1 envelope active dry yeast
• 2 cups warm milk
• 2 1/4 cups all-purpose flour
• 1 egg
• 3 tablespoons granulated sugar
• 3 eggs yolks
• 8 tablespoons butter, melted and cooled to room temperature
• 1 teaspoon vanilla extract
• 3 egg whites, beaten to soft peaks