Step 1In a medium mixing bowl, whisk together the cake flour, baking powder, salt, sugar and baking soda.
Step 2In a small bowl, mix the egg yolks and sour cream until smooth and whisk them into the dry ingredients.
Step 3Beat the egg whites until stiff but not dry. Stir approximately one-third of the egg whites into the sour cream mixture to lighten it, then gently fold the remaining egg whites into the batter. Bake according to manufacturer's instructions for your waffle maker. Serve immediately; they will soften on standing.