In a large bowl, whisk together flour, baking powder, salt and sugar. In a large measuring cup (4 cups or larger) or a medium bowl, whisk milk, egg yolks, vanilla and butter extract together. Make a well in the center of flour mixture and pour in the milk and egg mixture. Whisk until smooth. Whisk in melted butter. In a small bowl, whisk egg whites until they begin to stiffen. Fold egg whites into mixture.
Heat skillet over medium low heat. Add a small amount of butter to skillet. Pour or scoop the batter onto the skillet or griddle. I typically do 1/4 or 1/2 cup, depending on how big I want them.
When bubbles start to form, and bottom is slightly golden brown, carefully flip pancakes and brown the top. Repeat until all batter is used.
Serve hot with butter and maple syrup.
