Combine all of the dry ingredients in a large bowl and whisk them together. This ensures that you don't end up with pockets of baking powder in your waffles and helps them rise evenly in the waffle maker.
Whisk the milk, melted butter, and egg yolks in a separate bowl.
Mixing them well now means you need to stir the batter less later, which results in more tender, airy waffles.
Pour the eggs and milk mixture into the bowl with the flour mixture.
Stir just until combined and don't worry about getting out all the lumps.
Beat the egg whites until frothy, stiff peaks form. This can be done by hand, but it's definitely easiest with a hand mixer.
Fold egg whites into the waffle batter. Use a rubber spatula to gently fold the egg whites into the batter until they are combined.
Try not to knock out all the air that you just beat into your egg whites by folding or stirring too vigorously. It's okay to have a few lumps.
Fill your preheated waffle maker with batter. The batter will puff up and spread to fill the waffle maker while it cooks.
Serve warm! If you are making your waffles in batches, place the finished waffles on a wire rack while you make the next round of waffles before serving. Stacking them while still hot usually results in steam on the bottom of the waffles, making them less crisp.
The classic topping for waffles is butter and maple syrup, but other delicious toppings include nutella with sweetened whipped cream and fresh berries, fruit syrups or jams, apple pie filling, or even peanut butter!
Belgian waffles are typically a little sweeter and have more butter in the batter, which makes them richer than your standard buttermilk waffle.