Start the night before. Warm the milk and butter together until the butter melts
Allow to cool until just warm, not hot
In a large bowl combine four, yeast and sugar
Pour in the milk mixture and whisk until smooth. Cover loosely and leave at room temperature (or in fridge if house is not cool) overnight (8–12 hours)
Whisk into dough mixture the eggs and vanilla
Heat and grease your waffle iron. Cook according to your machine instructions until deep golden brown
Waffles can stay warm in a moderate oven or can be frozen and re-heated either in an oven or in the toaster