Wash the plums, pit them, weigh them, chop them and put them in a pot. Add the gelling aid and the juice of one lemon.
Stirring constantly, bring the fruit pulp to a boil. Then add the sugar and boil gently for about 5 minutes.
About 1 minute before the end of the cooking time, add the cinnamon and vanilla sugar.
Make a jelly test.
Pour about 2 mm of rum (bottom covered) into the jars. Fill the jars with the hot plum jam, close and put on the lid for about 5 minutes.
Preparation Tip:
The plum jam lasts about 12 months.