Heat an electric griddle or frying pan to 350 degrees F. In a large bowl, whisk together the flour, salt, baking soda, baking powder and sugar. Whisk together the egg whites and the buttermilk in a small bowl. In another bowl, whisk together the butter and egg yolks. Add the yolks and butter to the egg whites and buttermilk, whisk until combined. Pour the liquid ingredients on top of the dry ingredients. Using a whisk, mix the batter gently to combine. Stop as soon as you don’t see any more flour. The lumps will cook away.