For the banana tiramisu, mix the curd, yogurt, sugar and vanilla sugar. Whip the cream until stiff and fold in.
Prepare a cup of cocoa. Layer the biscuits in a mold and drizzle with cocoa. Put some cream on top, slice the bananas and press them into the cream, cover with cream.
Layer the sponge cake alternately with the cream to form a tiramisu. Finish with the cream and dust the banana tiramisu with cocoa before serving.