2) Separate the 2 eggs and put all the whites in a large bowl. In a large liquid measuring cup or medium bowl, whisk the egg yolks, milk, vanilla and 55g melted butter. Whisk the milk mixture into the flour mixture until a batter is formed. Take care not to over mix the batter.
3) Whip the egg whites with a hand-held electric mixer or whisk, until they just begin to hold a loose peak. Scatter the sugar over the whites and continue beating until they hold a soft peak. Fold a third of the egg whites into the batter to lighten the base, then fold in the remaining egg white. Gently fold in the chocolate chips.
4) Brush the inside surface of the waffle iron with butter. Pour in enough batter to barely fill each hole of the waffle iron; the amount will vary depending upon the size of the iron. (Take into consideration that the batter will spread once the lid is closed.) Close and cook until crisp and the waffle iron stops steaming, about 5 minutes.
5) Repeat with the remaining batter. If the waffle iron is well seasoned or nonstick it is not necessary to brush the inner surface each time before cooking the waffles.
6) Serve the waffles as they come off the iron, or keep warm by transferring to a rack set on a pan in a barely warm oven. Serve with syrup, jam, fresh fruit or yogurt. Or turn into a dessert with a scoop of ice cream.