Preheat the oven to 180 degrees top and bottom heat. Grease a large box cake tin (approx. 28 cm) and dust with flour. Alternatively, you can also use a springform pan, but the baking time may then have to be adjusted.
For the dough, beat the softened butter with the sugar until frothy, stir in the eggs one at a time. Slowly add the flour mixed with the almonds, baking powder, salt and baking cocoa; Finally fold in the grated chocolate.
Pour the dough into the prepared pan and smooth it out. Bake for about 50 to 60 minutes. Make a chopstick test. The cake can (and should) be a little moist inside. Let the cake cool in the pan, then turn it out. Cover with chocolate icing.