Mix 400 g flour and yeast. Melt 150 g fat, add 100 ml milk. Add 1 egg, lukewarm fat milk, 80 g sugar and 1 pinch of salt to the flour mixture and knead until smooth with a hand mixer. Cover and leave to rise in a warm place for about 30 minutes
Boil up 700 ml milk, 1 vanillin sugar and 80 g sugar. Stir in semolina, bring to the boil briefly, remove from the heat. Leave to swell for 5-10 minutes. Separate 5 eggs. Stir first sour cream, then 5 egg yolks into the semolina
Beat 5 egg whites until stiff and fold in. Let cool for 20-30 minutes. Wash the plums, cut lengthwise, pit
Grease a fat pan (approx. 32 x 39 cm; at least 3 cm high) and dust with flour. Knead dough briefly. Dust with flour, roll out on the fat pan, press up the edge by approx. 3 cm. Cover and let rise for about 15 minutes.
Pour 100 g Amarettini into a plastic bag, seal. Crumble finely with a rolling pin. Sprinkle crumbs and 50 g whole Amarettini onto the yeast dough. Spread semolina mixture on top. Put plums on top
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/gas: level 2) for approx. 50 minutes. Sprinkle the cake with 2 vanilla sugars and let it cool down. Before serving, sprinkle with sugar crystals and decorate with 3 tbsp. amarettini