Make a yeast dough from the dough ingredients and let rise. Roll out 2/3 of the dough on a greased baking sheet. Prick the dough several times with a fork.
For the quark topping, beat the egg white until stiff, mix the other ingredients together, carefully fold in the egg white. Smooth on the yeast dough.
Roll out 1/3 of the yeast dough and carefully transfer onto the quark topping. Quark should no longer be seen.
Melt the butter, knead with the flour, vanilla sugar and sugar to make crumbles.
Mix 20 ml of milk with 1 teaspoon of sugar and brush the yeast dough with it, pricking again several times with a fork.
From the still warm crumble dough (important, the crumble dough must still be warm), pluck small cookies, approx. 2 cm, with 2 fingers and spread them next to each other on the wet yeast dough (if the crumble dough is too crumbly, too dry, a little fat or 1 egg yolk admit).