Wash the cherries, take out pits, pour sugar over it and leave for the night for juices to come out.
Put cut vanilla legume into a pot. Boil cherries with sweet juices and leave it to cool off. Boil cooled jam again (this jam is more watery, so you have to boil it twice).
Pour a little bit of lemon juice and boil for about 10 to 15 minutes. Remove the pot from the fire and put grated black chocolate. Stir until chocolate melts. Pour hot jam into clean jars and put lids on. Overturn the jars and wait for it to cool off.