In large bowl whisk the flour, cornstarch, baking powder, and baking soda, and salt. Set aside.
In a medium bowl combine butter, buttermilk, vanilla, and egg yolks. Whisk until fully combined.
Add the wet ingredients to the dry ingredients, gently whisking (or use a fork) until just combined!
In a separate bowl add the egg whites. Beat on medium speed until soft peaks form. Then add the sugar to the egg whites and beat on medium/high speed until sugar has been fully mixed in.
Using a spatula, fold the egg whites into the batter. Do not overmix.
Preheat the waffle iron. Grease with butter or cooking spray. When ready, scoop 1 cup of batter onto the waffle iron… waffle irons differ in size so you may need more or less batter. Cook until golden brown, about 3 minutes and 30 seconds.
To keep waffles warm, place waffles in an oven preheated at 200°F. *