Put flour, sugar, vanilla sugar, salt, 1 egg and butter in flakes in a mixing bowl. Knead first with the dough hooks of the hand mixer, then with your hands to a smooth dough. Wrap in foil and chill for about 45 minutes. In the meantime, drain the cherries very well in a sieve and chop them finely. Mix the poppy seed filling and 1 egg.
Halve the dough. Roll out each piece of dough on a sheet of baking paper to form a rectangle (30 x 18 cm). Spread half of the poppy seed filling on each, leaving a free edge of approx. 1.5 cm on one long side. Sprinkle half of the cherries evenly on top. Roll up from the long side using the baking paper. Turn both rolls in sugar crystals. Press on the sugar. Put the rolls in a cool place for about 1 hour. Whisk the egg yolks and 1 tbsp. water.
Press on the sugar. Put the rolls in a cool place for about 1 hour. Whisk the egg yolks and 1 tbsp. water. Cut each roll into approx. 30 slices, place on 2-3 baking trays lined with baking paper and brush with egg yolk. Bake one after the other in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 12-14 minutes. Remove from the baking tray, place on a cake rack, allow to cool and pack in tins
waiting time approx. 1 1/2 hours