Separate eggs. Beat the egg whites, vanilla sugar and sugar with the whisks of the hand mixer until stiff. Stir in egg yolks and rose water. Carefully fold in starch, flour and almonds. Line a box form (11 x 30 cm; 1.75 litres capacity) with baking paper. Fill in sponge cake mixture and smooth it down.
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 15 minutes. Take out, turn onto a cake rack, remove baking paper, let the base cool down.
Soak gelatine in cold water. Chop the chocolate and melt over a warm water bath. Whip cream until stiff. Mix chocolate and quark. Dissolve gelatine. Stir in 5 tablespoons of the quark mixture, stir into the remaining quark. Carefully fold in the cream.
Coarsely chop the pistachios. Use a ball cutter to cut a few balls out of the melon, peel the remaining melon and cut it into thin slices. Wash, drain, clean and halve the strawberries. Divide the sponge cake horizontally into three.
Layer the sponge cake, curd cream and melon slices loosely on top of each other. Spread the top layer of sponge cake with cream and decorate with strawberries, melon balls and pistachios. Keep cool for at least 2 hours.