Sift flour, milk powder, sugar, yeast, and salt together in a large bowl.
Combine milk, water, and butter in a small saucepan over low heat. Heat until an instant-read thermometer inserted into the mixture reads 125 degrees F (52 degrees C), about 5 minutes; butter may not melt completely.
Pour milk mixture over flour mixture in the bowl; add eggs and vanilla extract. Mix until batter is thoroughly blended. Cover bowl loosely with plastic wrap. Refrigerate, 8 hours to overnight.
Preheat a waffle iron according to manufacturer's instructions.
Pour 1 cup batter onto the preheated waffle iron; close and cook until the iron stops steaming, about 5 minutes.