Preheat waffle maker.
Melt the butter and set it aside to cool slightly.
4 tablespoons (56g) unsalted butter
In a large bowl, whisk together the flour, cornstarch, sugar, baking powder, baking soda and salt.
2 cups (240g) all-purpose flour, ¼ cup (32g) cornstarch, 2 tablespoons (25g) granulated sugar, 1 teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
Crack the eggs into a medium bowl. Add the buttermilk, milk and vanilla. Whisk to combine. Slowly whisk in the melted butter.
2 large eggs, 1 ½ cups (360ml) buttermilk*, ¾ cup (180ml) milk, 1 teaspoon vanilla extract
Pour the wet ingredients into the dry and whisk until just combined.
Cook waffles according to manufacturer’s instructions, until crisp and golden. Waffles are usually done when just a small amount of steam is left escaping from the sides of the waffle iron. Serve immediately or keep warm in a 200 degree F oven (on a cooling rack placed on a baking sheet) while you cook the rest of the waffles.