You will have chop the chocolate by hand. Do not reduce the chocolate to a floury consistency. The size should be that of small peas. You want to have small pieces of chocolate in your cake after it baked. You can use chocolate morsels instead. But the quality of the cake improves if you use a good quality chocolate and not the regular chocolate morsels. Match the quality of your chocolate with the quality of your cacao. * I think cherries preserved in light sirup are best, but you can use whatever you can find. Sour cherries give a much more intense flavour than sweet cherries. You want about 300 g of cherries, but if you have a bit more or less it does not really matter. The only thing is, the cherries are largely responsible for the nice moisture of the cake. Cream butter with the sugar. Add eggs, one by one. Add the vanilla. Mix flour, hazelnuts, baking powder and add. Add rum, cinamon and cacao. (Hints for adding the cacao: If you use a machine, just add it here. If you do the cake by hand, you might want to reserve a bit of the sugar and mix it with the cacao to reduce the amount of lumps you have. Or mix the cacao with the other dry ingredients.) Fold in the chocolate. Carefully fold in the drained cherries. Put dough in well buttered form. You might consider dusting the form with whatever you use for this. I use a 26 cm (10 in) springform with the insert that makes a hole in the middle of the cake. This makes a nicely sized if a bit flat cake. If you want to use the flat insert, 1.5 times the recipe should be about right. Bake in preheated oven at 180ºC for 50 to 65 minutes. Do not overbake, one of the nice features of this cake is its moisture. Test with a wooden stick or a clean knife for doneness. If it comes out clean after you put it in the center of cake, the cake is done. But do not be deceived by the moisture of the cherries or the melted chocolate, so try two or three different spots, cleaning the knife or wooden stick after each use. I do not know why, but the baking time of this cake can vary considerably from oven to oven, and it also will depend on what form and overall quantity you use. Possible substitutions: Use walnuts instead of hazelnuts. Decorate cake with confectioner's sugar, or a chocolate glaze, and/ or whole nuts.