For 4 people
Wash the fruits and using a knife, make a notch to pit the plums.
Cut them so as to obtain small pieces of fruit.
Harvest the lemon juice using a grip press.
In a saucepan or pot, mix the fruits, lemon juice and crystallized sugar and then start cooking.
Once the preparation is boiling, continue cooking on low heat while stirring regularly with a spatula.
Meanwhile, prepare the jars by sterilizing them with boiling water.
After 30 minutes, check the cooking of the jam using a cold plate. The jam is ready if it freezes in contact with the plate. Otherwise, continue cooking for ten minutes.
Fill the jars with jam using a ladle.
Turn over the pot for a minute to let the air escape, and let it cool at room temperature.