Prepare the jam jars (cleaning …).
Prepare the plums and weigh exactly 900 g.
Put the plums, the water, the preserving sugar (type 2:1), the vanilla sugar and the ground cinnamon in a cooking pot and mix well.
If you work with a vanilla pod: cut the vanilla pod lengthwise & add to the mess. Don’t forget to discard the vanilla pod before filling the jam into the jam jars.
Bring the mess in the cooking pot to a boil. Mix thoroughly when cooking & let it bubble for 6 – 8 min … or even up to 10 min … (at least for the time according to the advice of your preserving sugar provider). The plums will dissolve & the plum mess will turn red when ready!
Then fill it at once in the waiting jam jars, close the screwtop & put the jam jars upside down.