Wash the plums well, stone them and place in a bowl. Sprinkle the preserving sugar on the plums and let stand for a while.
Chop the plums well with a magic wand! Add the vanilla sugar and season to taste with cinnamon (I use about 1 pinch for the amount).
Put the plum mixture in a large saucepan. The pot should only be half full (splashes and bubbles a lot)! Put the stove on full heat and heat the mass. Always stir well so that it doesn`t burn. When the mixture boils, let it simmer for about 5 minutes.
Then pour the boiling mass into clean glasses and close with a twist-off lid. Turn the glasses upside down and let them cool.