Finely chop the biscuits in the universal chopper. Melt butter. Mix butter and biscuit crumbs in a bowl, spread on half of a baking tray and press down firmly as a base. Put in a cool place for about 1 hour.
Bring 400 g spread to the boil in a saucepan and simmer for 8-10 minutes until thick and creamy. Remove cream from the stove and let it cool down while stirring occasionally.
Beat the mascarpone, sugar and vanilla sugar with the whisk of the hand mixer until thick and creamy. Whip 175 g cream until stiff, allowing the firming agent to trickle in. Fold the cream into the mascarpone cream.
Peel and slice the bananas. Spread caramel cream on the base and cover with banana slices. Spread the mascarpone cream on top and chill for about 30 minutes.
Stir 100 g spread with 25 cream until smooth. Cut the cake into pieces and sprinkle with caramel. Eat the cake quickly.