Separate eggs. Beat egg whites until stiff. Gradually pour in 100 g sugar. Stir in egg yolk. Sift the flour and starch over the egg yolk and fold in carefully. Line the bottom of a springform pan (26 cm Ø) with baking paper.
Pour in the dough and smooth it down. Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for approx. 20 minutes. Take out and let cool down. Cut the base once. Soak gelatine in cold water.
Mix kefir, lemon juice and zest, remaining sugar and vanillin sugar. Squeeze the gelatine, dissolve at low heat and stir into the kefir. Put it in a cold place. Drain apricots and dice.
Whip the cream until stiff and fold into the gelling cream. Fold in the apricot cubes as well. Place a cake ring around the lower cake base. Pour in the kefir cream, place the upper cake base on top and chill for approx. 4 hours.
Prepare the cake glaze with the apicot juice according to the package instructions. Spread on the top base and carefully place the lemon balm leaves on top. Makes about 16 pieces.