For the birthday cake sofa beat eggs, baking sugar and vanilla sugar until foamy. Then stir in water and oil alternately. Sift flour with cocoa and baking powder and stir in.
Spread the batter on a baking sheet lined with baking paper (38 x 25) and bake.
For the ganache, bring whipped cream to a boil and remove from oven, melt the dark chocolate in it. Refrigerate the ganache for a few hours. When cooled, cut 2 strips for the seat, cut 2 x for the back of the seat and carve 1 x the back round and assemble with sour cherry jam.
Push 3 cake supports into the backrest. Spread ganache all around the entire cake. Knead fondant until soft and cover the cake with it.
Decorate the birthday cake sofa as desired with self-modeled figures, etc.