Wash the plums, cut them in half and pit them

Wash the limes, cut them, remove pits.

Put limes and plums in a blender until they are cut in fine pieces

Put them in a pot, with the sugar and the fresh peppermint leaves (also finely cut)

Let it boil until it gets the right consistency. At the end add the rum, stir, let it boil for 2-3 minutes more and remove from heat.

Put the jam in sterilized jars, close them and let them cool upside down. Once they are cool you can store them. When you open a jar, keep it in the fridge.