Cream one-half cupfuls of butter with two cupfuls of sugar. Add the well beaten yolks of four eggs and one-half cupful of grated chocolate, melted. Mix in alternately one cupful of milk and two and one-third cupfuls of flour, sifted with four teaspoonfuls of baking powder and one-half teaspoonful each of cinnamon and salt. Add the stiffly beaten whites of the eggs and one teaspoonful of vanilla. Bake in loaf or layers.