First, whisk eggs and sugar until white and foamy.
Mix cocoa, rye bread, potato flour, and baking powder together and then mix it into the egg mixture.
Grease three cake pans with margarine and breadcrumbs.
Divide the batter into the three pans.
Bake the layers in a preheated oven at 170 degrees Celsius (338 degrees Fahrenheit) for 20-25 minutes. You can also grease a single 28 cm springform pan and pour all the batter in. In that case, bake it at 185 degrees Celsius (365 degrees Fahrenheit) for 50 minutes. Remember that the batter should be a bit spongy.
Whip the cream until stiff. Remember to stop whipping just before you think it's done. Whipped cream always thickens a bit more even after you've stopped whipping.
When the cake is cold, layer it with black currant jam and whipped cream: First, a layer of cake, then a layer of black currant jam, followed by a generous layer of whipped cream. Repeat with the remaining layers and optionally top the final layer of whipped cream with chopped chocolate.