Step 1

Preheat the oven to 200°F and set an oven rack in the middle position. Place an oven-safe rack on a baking sheet (this is to put the waffles on after cooking so they stay warm while you cook the others).

Step 2

In a large bowl, whisk together the flour, cornstarch, sugar, salt, baking powder, and baking soda.

Step 3

In a medium bowl, whisk together the buttermilk, egg yolks, and vegetable oil.

Step 4

Add the egg whites to the bowl of a stand mixer fitted with the whisk or beaters and beat to medium peaks (when you lift the beaters out of the bowl, the peaks should stand up firmly but curl over slightly at the tip).

Step 5

Add the buttermilk mixture and melted butter to the flour mixture and whisk until smooth. Using a rubber spatula, fold in the beaten egg whites until just evenly combined.

Step 6

Preheat the waffle iron and cook the batter according to the manufacturer's instructions, or until the waffles are golden brown. The waffles will seem a little flimsy and limp straight out of the waffle iron, but they will crisp up almost immediately once off the heat. Serve immediately or place on the prepared rack/baking sheet and keep warm in the oven while you cook the remaining waffles.

Step 7

Make-Ahead/Freezing Instructions: To freeze, let them cool completely after cooking, then place them in a single layer on a baking sheet to freeze individually. Once frozen, transfer the waffles to a freezer-safe bag or container, separating layers with parchment paper if needed. To reheat, simply toast the waffles (using a light setting) directly from the freezer until they're warm and crispy.