For the yeast dough, warm the milk lukewarm. Crumble the yeast into it and dissolve it. Put 500 g flour, sugar, vanilla sugar, 1 pinch of salt, 50 g butter and egg in a bowl. Pour in the yeast milk and work everything into a smooth dough with the dough hooks of the mixer. Cover and leave to rise in a warm place for about 45 minutes.
For the Amarettini crumbles, grind finely in the universal shredder. Mix with 100 g flour, brown sugar and cinnamon. Add 75 g butter in pieces. Use the dough hooks of the mixer to make crumbles and chill for about 30 minutes.
Wash, halve and stone the plums. Line the fat pan of the oven (approx. 32 x 39 cm) with baking paper. Knead the yeast dough again briefly and roll out rectangularly. Place in the fat pan and press evenly into the corners. Cover and leave to rise for another 15 minutes.
Spread the plums on the dough with the cut surface facing upwards and press in a little if necessary. Sprinkle Amarettini sprinkles over it. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) for approx. 25 minutes.