The orange-chocolate combination gives this old English recipe a very distinguished flavor. Not the easiest cake to make but well worth the effort.
Cream the butter and add to it the sugar and grated rind. Add the beaten egg yolks. Sift together the flour, salt, and baking powder. Add the dry ingredients alternately with the milk to the creamed mixture. Fold in the egg white, beaten until stiff.
Divide the batter in two, and to one part add the melted chocolate.
Put by tablespoonsful – alternating dark and light batter – into three greased and lightly floured 10-inch cake pans. Bake in a 375 degrees F oven for 20 to 25 minutes, or until the cake springs back when lightly touched in the center.
Cool in the pans for 10 minutes, then turn out on racks.
Beat all together until smooth. Fold in the stiffly beaten egg white. Spread this icing on the layer being used for the top of the cake.
While the icing is soft, sprinkle the top iced layer with finely shaved unsweetened chocolate, using ½ square.
To the remaining icing add 2-½ squares chocolate, melted over hot water. Spread this icing thickly between the layers and on the sides of the cake.