Before going to bed, combine the dry ingredients and stir in the milk, then the butter. The mixture will be loose. Cover the bowl with plastic wrap and put it in your oven with the oven light on.
In the morning, brush the waffle iron lightly with oil and preheat it. Separate the eggs and stir the yolks into the batter. Beat the whites until they hold soft peaks.
Stir them gently into the batter. Do not overmix. It's okay if there are clouds of whites that are not integrated into the mixture.
Spread a ladleful or so of batter onto the waffle iron and bake until done. It's best if you serve them immediately, but if you can't do that, they'll keep in the oven for a few minutes.
Serve with maple syrup. And for heaven's sake, make sure the syrup is hot.