Heat the milk till it’s very hot. Place it in a large mixing bowl (you’ll need lots of room for expansion), and add the butter, maple syrup, salt, and vanilla. Stir till the butter melts and the mixture has cooled to lukewarm. Add the eggs, flour, and yeast, stirring to combine; it’s OK if the mixture isn’t perfectly smooth. Cover with plastic wrap, and let rest at room temperature for 1 hour; the mixture will begin to bubble. You can cook the waffles at this point, or refrigerate the batter overnight to cook waffles the next day. (Make SURE it’s in a bowl large enough for it to at least double in size!)