In a bowl, whisk the yeast into the milk, then add the sugar and set aside.
In a very large bowl (the dough will triple in volume), put the flour. Make a well in the center, then add the eggs and melted butter.
Mix by gradually adding the milk, until the dough is smooth and lump-free.
Add the vanilla extract and mix.

Cover the bowl with plastic wrap and let it rest in a temperate place for 2 hours.
The dough will be thick and elastic, it won’t stretch in the waffle iron like regular dough. You’ll need to spread it a bit with a spatula.
Cook the waffles as suggested in your waffle iron’s manual, until they are golden brown.