Line a baking tray (approx. 35 x 40 cm) with baking paper. Separate the eggs. Beat the egg whites, 4 tbsp. cold water and salt until stiff, adding 100 g sugar and 1 vanillin sugar. Beat the egg yolks separately into the mixture. Sift flour, starch, cocoa and baking powder into it and fold in. Spread on the baking tray. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for about 15 minutes. Turn out onto a damp tea towel, remove baking paper. Let the sponge cake cool down
Halve the sponge 1 x crosswise to 2 smaller plates. Fold 4 approx. 8 x 60 cm rails from aluminium foil, place 2 around each plate and close them.
Soak the gelatine in cold water. Mix quark, 100 g sugar, 1 vanillin sugar and lemon peel. Squeeze the gelatine and dissolve over a mild heat. Stir in 2-3 tbsp. quark, then stir into the rest of the quark. Whip cream until stiff, fold in. Spread on the plates. Spoon the berries onto them, if necessary pull them spirally through the cream with a fork. Refrigerate for at least 4 hours.