1. | In a large mixing bowl, dissolve yeast in warm water. |
2. | Add sugar; let stand for 5 minutes. |
3. | Add the milk, egg yolks, butter, and oil (refrigerate egg whites). |
4. | Combine flour and salt; stir into the milk mixture. |
5. | Cover bowl and refrigerate overnight. |
6. | Let egg whites stand at room temperature for 30 minutes. |
7. | In a small mixing bowl, beat egg whites until stiff peaks form. |
8. | Stir batter; fold in egg whites. |
9. | For each waffle, pour the batter by 1/4 cupfuls into a preheated waffle iron; bake according to manufacturer's directions until golden brown. |