Wash, halve and stone the plums. Cut the upper tips. Mix marzipan, 1 egg and 50 g sugar with the whisk of the hand mixer. Mix quark, milk, oil, remaining sugar, vanillin sugar, salt and remaining egg with the dough hooks of the hand mixer.
Mix flour and baking powder and knead with the dough hooks of the hand mixer. Knead the dough again with floured hands. Roll out to a thickness of approx. 1/2 cm on a floured work surface. Cut out about 10 circles (12 cm Ø).
Place circles on two baking trays lined with baking paper. Spread plums in a circle on top. Pour marzipan into a piping bag with a star-shaped spout and spray a tuff on each cake in the middle.
Bake in the preheated oven one after the other (electric oven: 175 °C/ gas: level 2) for approx. 25 minutes. Whisk the egg yolk and cream for the coating. Spread the edges of the cakes with the egg yolk cream approx. 5 minutes before the end of the baking time.
Remove from the oven, allow to cool on a cake rack and dust with icing sugar.