For the dough melt butter, let it cool down. Separate 5 eggs. Beat 5 egg whites and 1 pinch of salt until stiff, add 125 g sugar. Stir in 5 egg yolks individually. Mix flour, baking powder and cocoa, fold in. Add butter. Fold in beaten egg white. Pour into a springform pan (26 cm Ø) lined with baking paper at the bottom. Bake in a hot oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for about 25 minutes, let cool down.
For the cream, divide the chocolate into pieces and melt in a hot water bath. Let it cool down. Separate 5 eggs. Beat 5 egg whites until stiff, while pouring in 50 g sugar. Whip the cream until stiff. Whip 5 egg yolks and vanilla sugar in a hot water bath. First stir in chocolate and 2 tbsp. cream, then fold in the rest of the cream and beaten egg whites one after the other in portions. Chill the mousse for about 30 minutes.
For the compote, drain the cherries and collect the juice. Mix starch and 3 tablespoons of juice. Boil up the rest of the juice and 2 tablespoons of sugar. Stir in starch, simmer for about 1 minute. Add the cherries, cool down.
For the edge, chop the chocolate coating, melt in a hot water bath and spread on a smooth surface. Allow to dry and push together into rolls.
Cut the sponge in half. Cover the bottom with a cake ring. Spread the compote on top and spread half of the mousse on top. Place the upper cake layer on top. Spread the rest of the mousse dome-shaped on top. Chill for about 1 hour.
Pass the jam through the sieve. Spread the edge of the cake with the jam and press the chocolate rolls on. Dust the cake with cocoa.
Spread the liquid couverture on an upside-down baking tray or on a marble plate. As soon as it begins to set, use a wide spatula to form long rolls.