Preheat oven (electric cooker: 225 °C/circulating air: 200 °C/gas: see manufacturer). Line a baking tray with baking paper. Separate the eggs for the sponge cake. Beat the egg whites with 1 pinch of salt until stiff, adding 100 g sugar.
Mix the espresso with 3 tablespoons of cold water. Stir the egg yolk briefly into the egg whites. Sift the flour and 4 tbsp. cocoa over the egg whites and fold in. Spread the dough on the tray. Bake in a hot oven for about 8 minutes.
Take out the sponge cake. Turn onto a sugared tea towel immediately. Remove the baking paper. Roll up the sponge cake. Let the sponge roll cool down.
For the filling, let the raspberries thaw. Mix quark with 2 tablespoons of sugar and chai latte powder. Whip cream until stiff, fold in. Roll out the cooled sponge cake. Spread the cream on top, leaving an approx. 5 cm wide rim on the outer long side.
Spread raspberries over the cream. Roll up the sponge cake again using the cloth. Place the roll on a plate. Chill for at least 30 minutes. Dust with cocoa before serving.