For the cake: Cream butter & sugar together. Add beaten egg yolks.
Sift together flour, soda, and baking powder.
Add the dry ingredients alternately with milk to the creamed mixture.
Add the cocoa mixture and vanilla and mix well
Beat the 3 egg whites until stiff. Fold into chocolate cake batter.
Bake in cupcake papers in 350-degree oven.
For the icing: Slowly heat the first two ingredients to paste in a medium sized saucepan on the stove, stirring constantly with a whisk. Let cool.
With an electric mixer beat in 1 stick of butter, 1 stick of margarine, the sugar, the vanilla and the cocoa id desired.
Note: For chocolate icing add cocoa to desired darkness.