Drain the cherries in a sieve. Collect the juice. Cream butter, liqueur, 1 packet of vanilla sugar and sugar with the whisk of the hand mixer. Stir in the eggs one by one.
Mix flour and baking powder and stir into the dough. Halve the dough. Stir cocoa and milk into one half of the dough. Fold in half of the cherries. Grease a ring cake tin (2 litres capacity) and dust with flour.
Spread half of the light-coloured dough in the mould and smooth it down. Add half of the dark dough and smooth it down as well. Spread the rest of the dough on top as well. In a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see
manufacturer) bake for approx. 1 1/4 hours (stick sample). Cover with foil after 1 hour if necessary. Remove the cake, let it cool down in the tin for about 10 minutes, then turn out onto a cake rack and let it cool down.
In the meantime, stir 3 tablespoons of juice with starch until smooth. Boil up the rest of the juice and 1 sachet of vanilla sugar. Add the starch mixture and simmer for about 2 minutes while stirring. Add cherries and stir in.
Pour the compote into a bowl and let it cool down. Roughly chop the chocolate, melt over a hot water bath and spread on the cake. Add the stewed cherries. Coarsely chop the pistachios and decorate the cake with them.