1. In large bowl, whisk together flour, sugar, baking powder and salt. In separate bowl, whisk together milk, melted butter, egg yolks and vanilla; stir into flour mixture just until moistened.
2. Using electric mixer, beat egg whites until stiff peaks form; fold into batter (do not overmix).
3. Preheat CRUX Double Rotating Belgian Waffle Maker. Ladle 3/4 cup batter into each waffle iron to cover about two-thirds of the grid surface; close lid after each addition. Cook for 4 to 5 minutes or until steam stops emerging from waffle irons, and waffles are golden brown and crisp. Repeat with remaining batter.