Whisk together the flour and baking powder in a large bowl.
In a separate bowl, add the butter, milk, and egg yolks, stirring to combine.
In a third bowl, use a hand mixer to beat the egg whites until soft peaks form.
Pour the milk mixture into the flour mixture and stir with rubber spatula until just combined. Add the beaten egg whites and gently fold to combine.
Heat an 8-inch (20cm) nonstick skillet over low heat. Pour 1 ½ cups of pancake batter into the skillet, smooth out the top, then cover with a lid. Cook until golden brown on the bottom and a toothpick inserted into the center comes out clean, about 20 minutes. Transfer the pancake to a plate and repeat, making 5 more pancakes with the remaining batter.