2-1/4 tsp. Active Dry Yeast
1 tsp sugar
1/4 cup warm water
1/4 cup unsalted butter
2-1/4 cups warm lowfat milk
3 cups unbleached, all-purpose flour
1 cup cornstarch
3 eggs, separated
1/2 cup granulated sugar, divided
1 tsp. salt
2 tsp. pure vanilla extract
Stir yeast and sugar into warm water in a small bowl; let stand until foamy, about 3 to 5 minutes.
Warm butter and milk together in a small saucepan over low heat so that the butter melts but the milk does not exceed 110°F (43°C)[If mixture is hotter than that allow to cool to 105°F before continuing]. Reserve.
Combine the flour and cornstarch in a separate bowl; reserve.
In a large bowl, whisk together the egg yolks, milk and butter mixture, yeast mixture, 1/4 cup of the sugar, salt and vanilla. Stir in the milk and flour/cornstarch mixture alternately, ending with the flour. Wrap in plastic and let stand until mixture is doubled in volume, about an hour. Preheat the Waffle iron.
Whip egg whites until frothy, and then add remaining 1/4 cup of the sugar. continue to whip until firm peaks form. Carefully fold whites into waffle batter using a large rubber spatula.
When iron is ready, Pour batter onto the centre of the lower grid; spread batter using a heatproof spatula to 1/2 inch of the edge of the grid. Close lid of iron and bake. Remove baked waffle with a fork, repeat with rest of batter.