2 cups all-purpose flour
1/2 teaspoon salt
2 tablespoons sugar
1-1/2 teaspoons baking soda
1-3/4 cups buttermilk
2 eggs, separated
4 tablespoons (1/2 stick) butter, melted and cooled
1/2 teaspoon vanilla extract
Vegetable oil for brushing on waffle iron
Combine flour, salt, sugar, and baking soda.
Mix together the buttermilk and the egg yolks. Stir in butter and vanilla.
Brush the waffle iron lightly with oil and preheat it.
Stir the buttermilk mixture into the flour mixture.
Beat the egg whites with a wire whisk or electric mixer until they hold soft peaks. Stir them gently into the batter.
Spread a ladleful or so of batter onto the waffle iron. Bake until the waffle is golden brown, usually 3 to 5 minutes. Serve immediately or keep warm for a few minutes in a low oven.