Separate the eggs for the sponge cake. Beat the egg whites and 1 pinch of salt until stiff, adding 100 g sugar. Stir in the egg yolks one by one. Sift flour and baking powder on top and fold in. Fold in 50 g chocolate. Spread the mixture on a baking tray (35 x 40 cm) covered with baking paper. Bake in a hot oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer) for about 10 minutes. Let it cool down.
For the compote, wash and stone the plums. Boil up with 100 ml cherry juice, cinnamon, 1 packet vanilla sugar and 100 g sugar while stirring. Mix the starch with 100 ml juice, pour into the plums while stirring and simmer for about 2 minutes at low heat. Let it cool down.
For the cream, soak gelatine in cold water. Mix the quark and 100 g sugar. Whip 200 g cream until stiff. Squeeze gelatine well and dissolve in a small pot. First stir 2-3 tablespoons of cream into the gelatine, then stir everything into the rest of the cream. Fold in cream and 50 g chocolate. Remove cinnamon from the compote. Fold the compote in streaks into the cream.
Halve the sponge cake crosswise, place a rectangular cake frame around one half, spread the cream on top. Place the rest of the sponge cake on top. Chill the cake for at least 3 hours.
Whip 300 g cream with 1 sachet of vanilla sugar until stiff and fill into a piping bag with perforated spout. Then squirt the cream as tuffs close together on the slices.