Separate eggs, beat egg whites and 2 tablespoons of water until stiff. Gradually add 75 g sugar, salt and 1 packet of vanilla sugar. Add the egg yolks and stir carefully. Mix flour, baking powder and starch, sieve onto the egg-sugar mixture and carefully fold in as well. Spread the dough on a baking tray (32 x 39 cm) lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 10-15 minutes.
In the meantime soak the gelatine. Drain the apricots and cut into cubes. Stir the quark, lemon juice and zest, 75 g sugar and 1 packet of vanillin sugar until smooth. Squeeze the gelatine, dissolve and stir into the quark mixture drop by drop. Fold in the apricots and chill. Turn out the sponge cake onto a damp tea towel, remove the baking paper and wrap the corners of the tea towel. Let it cool down a little. In the meantime, whip the cream until stiff and fold in as soon as the quark mixture begins to gel. Cut the sponge cake in half crosswise. Cover 1 half of the dough with a cake frame. Add the quark mixture and smooth it down. Place 2 halves of the dough on the quark mixture and press down lightly.
In the meantime, whip the cream until stiff and fold in as soon as the quark mixture begins to gel. Cut the sponge cake in half crosswise. Cover 1 half of the dough with a cake frame. Add the quark mixture and smooth it down. Place 2 halves of the dough on the quark mixture and press down lightly. Chill for at least 4 hours. Cut into 8 pieces. Dust with icing sugar and decorate with lemon balm