Warm up the milk. Crumble the yeast and dissolve in it. Put flour in a bowl. Add sugar, butter in flakes and salt. First stir in the yeast milk and then the egg. Then knead everything into a smooth dough. Cover the dough and put it in the fridge overnight or leave it in a warm place for about 30 minutes.
Grease a springform pan (26 cm Ø). Dice marzipan into small cubes. Mix with plum jam and sour cream. Roll out the dough on a little flour to a rectangle (approx. 30 x 42 cm). Spread the plum puree mixture over it, leaving a rim of approx. 3 cm wide all around. Roll up from the long side and cut into approx. 14 slices (each approx. 3 cm). Place the slices in the prepared mould, cover and leave to rise in a warm place for approx. 30 minutes
Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for approx. 40 minutes. Let cool down a little. Remove from the mould. Heat up the jam and pass through a sieve. Coat the cake with it. Dice plums finely. Sprinkle the plums, pistachios and sugar crystals on the cake's edge