Butter, sugar and flour are mixed. Over the resulting composition add the beaten egg whites, cocoa, rum essence, ground walnuts and baking powder. Mix the dough well and place it in a tray in which I have previously placed baking paper. Bake in the oven for about 30 minutes.
Spread the icing (powdered sugar mixed with the yolks) over the baking tray and bake for another 10 minutes.
Over the baked cake, after it has cooled down a bit, grate the chocolate or pour the melted chocolate with a spoon.
I prefer grated chocolate, it's more attractive that way. Now I had kinder chocolate in the fridge and melted it in a little milk on the fire.