First dissolve the yeast in the lukewarm milk with the vanilla sugar.
Sift the flour into a bowl. Add the quark, egg, sugar and butter. Add the yeast that has now dissolved and work everything into a smooth dough. Let the dough rise in a warm place. In the meantime, preheat the oven to 175 °.
Shape the dough into small balls, brush with egg yolk, sprinkle with sugar-coated sugar and place the cakes on a baking sheet lined with baking paper. Bake for about 20 minutes.