Defrost the cherries in a sieve, collecting the juice. Knead the flour, 100 g sugar, vanillin sugar, 1 pinch of salt, cocoa, 1 tablespoon cold water, 1 egg and butter in pieces first with the dough hooks of the hand mixer, then with your hands to a smooth dough.
Roll out the short pastry on a floured work surface until round (approx. 26 cm Ø). Place the dough in a greased springform pan (22 cm Ø), dust with flour, using a dough roller, press the edge lightly.
Chill the short pastry for about 30 minutes.
Prick the base several times with a fork and bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 20 minutes. Remove the base from the oven and let it cool down.
Soak gelatine in cold water. Roughly chop the chocolate. Heat 200 g cream and remove from the heat. Squeeze the gelatine and dissolve in it. Melt the chocolate in it and let it cool down while stirring occasionally until it binds easily.
Whip the rest of the cream until stiff and carefully fold into the chocolate cream. Fold about half of the cherries into the mixture. Spread the cream on the base and chill overnight.
Boil up the cherry juice, the remaining sugar and the cherry juice. Mix starch and 1 tablespoon of water. Bind the cherry juice with it, bring to the boil again. Stir in remaining cherries, remove from heat and let cool.
Remove the cake from the tin, cut into pieces and decorate with the cherry compote.