Sift together the first 5 ingredients and set aside. Beat egg yolks until thick and lemon-colored. Beat in melted butter. Add sour cream and buttermilk. Mix only until blended. Mix with dry ingredients. Beat egg whites until the stand in soft stiff peaks: fold into the mixture. Por batter into waffle iron and bake 4-5 minutes or until steam subsides. These waffles can be served hot or cold with jam (Norwegian style).