Beat egg yolks in a large bowl until the sugar is thoroughly mixed and the yolks are thick and sunny colored. Add the milk, cooled melted butter, and vanilla extract and stir until combined. Then add all at once flour, baking powder, and salt. Mix well, but be sure not to overmix (overmixed batter will be frothy with lots of bubbles). If the mixture is too thick, add more milk until the mixture resembles that of thick pudding.
In a separate bowl, using a mixer, beat egg whites until stiff. Using a rubber spatula, gently fold the egg whites into the batter. DO NOT MIX.
Bake, following the instructions of your waffle maker until golden brown. Please note, these waffles rise and expand considerably so use the least amount of batter needed for desired results. For those using a lock-lid waffle maker, this is especially important. For results that most resemble Mickey waffles as served at Disney World, use a Belgian waffle maker.
Serve with a variety of toppings, including butter, powdered sugar, syrup, chocolate sauce, chocolate chips, whipped cream, strawberries or other fruits, even ice cream and sprinkles.