Prepare the dough from flour, sugar, baking powder, egg yolk, softened butter, and cocoa. Divide the dough into two parts and place it in the freezer for half an hour.

Meanwhile, prepare the filling. Whisk the egg whites until stiff peaks form. Mix the quark with egg yolks, sugar, and cornstarch, then gently fold in the whisked egg whites.

Grate one half of the dough onto a cake pan or a smaller baking sheet lined with parchment paper using a coarse grater. Layer the prepared filling and then grate the second half of the dough over it.

Bake at 180 °C for 20 minutes, then reduce the temperature to 160 °C and bake for another 20 minutes. Let it cool completely.