Puree the cherries and mix with the preserving sugar. Chop up the marzipan mixture and add. Bring the mixture to the boil while stirring and cook according to the instructions on the packet (about 3-5 minutes). Chop the chocolate and stir in well.
Make a gelling test, i.e. put a few drops of the jam on a small plate, if the jam does not run, the consistency is okay.
Fill the jam to the brim in twist-off glasses, close tightly and turn upside down.