Combine flour, cornstarch, salt, baking powder and baking soda in a medium bowl.
In another bowl, whisk together the buttermilk, vegetable oil, milk and egg yolks.
Add the sugar and vanilla beat until glossy.
Beat the egg whites until soft peaks form.
Add the liquid ingredients to the dry ingredients and mix until just blended (there may be a few lumps, which is okay). Fold in egg whites until just mixed in.
Pour batter into a preheated waffle iron and bake until browned and crisp.