Cocoa and quark Russischer Zupfkuchen

Set aside 200 g butter to soften for 20 minutes, keeping the rest cold. Crack eggs, beat to combine whites and yolks, then actually weigh the required net amount without shells. Reserve 50 g for pastry and 150 g for filling. Grease a springform tin 26 cm across and 6 cm high with 5 g butter. Mix flour, cocoa, 150 g sugar, baking powder and salt. Cut the 150 g cold butter into small pieces and add it with the pastry eggs. Bring together quickly without prolonged kneading. Weigh dough and divide into equal halves: press one into a base and 3 cm side, keeping the other cold.

Beat reserved filling eggs with 150 g sugar and reserved softened butter. Add quark, vanilla sugar and pudding powder without extra milk. Spread on the base. Tear reserved cocoa pastry into pieces and place over filling with gaps. In a conventional oven preheated to 180 °C, check browning after 45 minutes, then bake for about 15 minutes more until edges set and centre barely wobbles. Cover loosely with foil if needed. Cool in the tin on a rack for 90 minutes, then chill for at least 120 minutes before unmoulding and cutting.