Break the marzipan into small pieces. Mix flour and baking powder, add to the marzipan with the remaining ingredients and knead into a smooth dough with your hands. Cover the dough and chill for at least 2 hours. Quarter the dough. Form a quarter into a roll on a floured work surface and divide into 14 pieces. Make an approx. 12 cm long roll from each piece and shape into a croissant. Process the rest of the dough in the same way.
Place on two baking trays lined with baking paper. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for 10-15 minutes one after the other. Let cool down on a rack. Mix rum and icing sugar for the icing. Spread the icing on the croissants and sprinkle with chocolate flakes. Results in 56 pieces