Mix eggs and sugar with the whisk of the hand mixer until foamy, stir in the quark, cream and starch one after the other. Halve the dough and stir in the cocoa powder under one half.
Grease a springform pan (26 cm) and dust with flour. Put the two doughs alternately in the form in blobs. Pull through with a fork to create a marble pattern.
Bake in a preheated oven (electric stove 175 ° C, fan oven 150 ° C, gas mark 2) for 50-60 minutes. Let rest for 15 minutes in the switched off oven. Loosen the edge of the cake with a knife. Allow to cool in the mold.