preheat waffle iron

in a large bowl, whisk together the flour, sugar, cornstarch (if using), baking powder, and salt until well combined

In a medium bowl, whisk the eggs until combined, and then whisk in the milk. Gradually whisk in the butter

Pour the liquid ingredients into the dry ingredients and whisk gently just until the batter is evenly moistened. It's fine if some small lumps remain. Give the batter a couple of folds with a rubber spatula to ensure that there aren't any pockets of flour.

Pour a generous .5 cup of the batter into the center of the waffle iron. Use the rubber spatula to even it out and distribute it slightly. Close the lid and bake the waffle to the desired doneness.

Remove the waffle and serve it immediately before baking the remaining batter. Or set it on the wire rack and slide the baking sheet into the oven to keep the waffle warm. Bake the remaining batter, transferring each waffle to the rack in the oven