Step 1Place warm water in a large mixing bowl (the batter will double in volume), and sprinkle in the yeast. When dissolved, stir in milk, butter, salt, sugar, flour and eggs, and beat until smooth and blended. Cover the bowl with plastic wrap and refrigerate overnight.
Step 2Just before cooking the waffles, beat in the baking soda. The batter will deflate and become about as thin as soft yogurt. Cook the waffles according to the manufacturer's instructions for your waffle maker.