Remove stones from plums and cut in half. Toss the plums, cinnamon, star anise and vanilla pod into your preserving pan.
Finely chop the chili and remove the seeds. Add this to the pan along with the zest of the lemon and all the juice. Add the sugar and heat slowly to dissolve.
Now ramp up the heat and boil madly for about 10 minutes or until a spoonful of the jam sets to a crinkle on a chilled saucer.
Pot into sterilised jars.