Separate eggs. Beat the egg whites and 3 tablespoons of cold water with the whisk of the hand mixer until stiff, adding 120 g of sugar. Add egg yolks one after the other and stir in. Mix flour, starch, cocoa and baking powder, sieve onto the egg yolks and fold in carefully.
Grease the bottom of a springform pan (26 cm Ø) and dust with flour. Fill in sponge mixture and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 18-20 minutes. Let the sponge cake base cool down in the mould on a cake rack.
Soak gelatine in cold water. Cut the mango flesh from the stone, then peel. Cut 1/2 mango (approx. 250 g) into cubes (use edges). Mix quark, vanillin sugar, 100 g sugar and lemon juice. Dissolve squeezed gelatine in a small pot. Stir in 4 tablespoons of cream, then stir into the rest of the cream. Chill the cream for 10-15 minutes until it starts to gel. Whip cream until stiff and fold in. Finally fold in mango cubes.
Remove the sponge cake from the mould and enclose it with a cake ring. Spread the cream on top and chill for about 30 minutes. Cut the rest of the mango meat into thin slices. Cover the cake with mango slices in a dense fan shape and chill for another 3-4 hours. Before serving, heat the jelly, stir until smooth and brush the mango slices with it.