How to make
Wash the plums, halve them and remove the pits. Arrange them in a deep oven dish, packed tightly next to each other. Sprinkle with sugar, then arrange a 2nd layer of plums and sugar again. Leave it to sit in a cool area for a few hours or overnight.
Then top off with water in the oven dish, add the cinnamon and cloves. Put the oven dish in the oven. Wait for the syrup to come to a boil and turn it off. Leave the jam until it cools.
The next day, return it to the oven to heat up but without boiling. Repeat this process a 3rd day, at which point the syrup should be plenty thick.
Mix the jam with the citric acid and distribute into jars, while also sprinkling toasted walnuts in between the plums. Close the jars and sterilize for 5 min.
