In a medium bowl, whisk together all-purpose flour, cornstarch, sugar, salt, baking powder, and baking soda. Set aside.
In a large bowl, whisk together milk, buttermilk, oil, eggs, and vanilla. Add the dry ingredients to the liquid mixture, and gently whisk together until just incorporated and a few lumps remain. Set aside for 30 minutes.
Preheat waffle iron and lightly grease with melted butter or oil. Pour in desired amount of batter, making sure not to overfill, and cook according to manufacturer instructions.
To freeze waffles, cool completely to room temperature and store in a freezer safe container. To consume, place frozen waffle on a baking sheet and warm in a 300°F oven until thoroughly heated, about 10 minutes.