Drain the mandarins on a sieve. Defrost the raspberries, mash them and pass them through a sieve. Boil up 3/4 litre of milk. Mix the rest of the milk with pudding powder and sugar, pour into the boiling milk and bring to the boil again while stirring.
Cut the pudding in thirds. Mix one third with the raspberry puree. Set aside a few mandarins for decoration. Mix the remaining mandarins with the second third of the pudding. Spread the last third of the pudding on glasses.
Layer the raspberry pudding on top and finally place the mandarin pudding on top. Decorate with mandarins, crumbled bark chocolate and lemon balm. Keep cool until serving.