Roughly chop Santa Claus chocolate. Warm the cream. Add chocolate, coffee powder, rum and fat to the cream and stir until smooth. Leave to cool. Rinse a box mould (approx. 30x11 cm; 1 1/2 litre capacity) with water and line it with foil. Stir the chocolate mixture again.
Spread the bottom of the box mould approx. 1/2 cm high with the chocolate mixture and cover with biscuits. Fill the mould layer by layer. Refrigerate overnight in the fridge. Turn over the cake with the help of the foil. Cut diamonds out of the cardboard, place them on the cake and dust with icing sugar and cocoa as desired. Decorate with brittle
waiting time approx. 14 hours