How to make
Put the softened butter (at room temperature) in a bowl, add the powdered sugar and beat with a mixer, until a smooth mixture is obtained. Add the two yolks and continue beating for another 5 minutes. Pour in the milk in a thin stream.
Sift the flour along with the baking powder and a pinch of salt. Add it in portions to the liquid mixture, while stirring with a spoon. Add the chopped walnuts. Beat the egg whites, until a white mixture is obtained with a pinch of salt for 5 minutes. Add them to the sponge cake mixture.
Flavor with lemon peel. Grease and flour a cake tin for a classic sponge cake. Pour the mixture and bake the sponge cake with walnuts at 360°F (180°C) in a preheated oven. Check it with a wooden skewer, in order to see if it is fully baked. Turn the finished sponge cake onto a wire rack and cool it.
Break the chocolate into a pot, add the butter and melt it in a water bath. Pour it over the Walnut Sponge Cake!
Appetizing Walnut Sponge Cake with Chocolate! Enjoy!