Wash, stone and chop the plums. Cut the vanilla pod in half lengthwise and scrape out the pulp with the back of a knife. Mix 1 kg pulp, cinnamon stick, jam sugar, vanilla pod and pulp in a pot and let it stand for about 1 hour. Bring everything to the boil and simmer for 4 minutes. Add orange liqueur shortly before the end of the cooking time.
Remove cinnamon stick and vanilla pod. Puree the jam briefly with the chopping stick and make a gelling test. Pour the jam into clean, well sealed jars (preferably with twist-off lids). Close the jars well and turn them upside down for about 5 minutes, then let them cool down
Waiting time 1 hour