There is no recipe, as such. Take a big jar or tin of cherries, black if possible, but morello will do. Put juice in a pan with sugar to taste and boil slowly for about 5 mins to reduce then add a teaspoon of cornflour and stir, then a couple of tablespoons of kirsch, to taste, and stir cherries in, reserving a few for decoration if you want. Place cake at bottom of dish and sprinkle with kirsch, then pour cherries + reduced juice over cake. Cover with custard which has been allowed to cool, then whipped cream on top. Decorate with remaining cherries or grated black chocolate, or both. Easy peasy.