For this jam, use any variety of plums so long as they are ripe and juicy. If you're short of a few plums, top up the weight with an equal quantity of peeled and cored apples. As plums are high in pectin, no additional acid is required to help the jam set. To test the setting point of the jam, place a teaspoonful on a cold saucer and allow it to cool, then run a finger through it. If the trail remains, and the surface wrinkles slightly, rest assured, it will set.
- Remove any stalks and place the plums and water in a deep saucepan.
- Stew slowly until the fruit has broken down - about 20 minutes.
- Add the sugar and stir until dissolved, then return the jam to the boil.
- As the stones rise to the surface, remove them to a sieve suspended over the saucepan. This will allow any liquid to drip back into the jam.
- Cook for about 10 minutes to reach the setting point, then skim and pour the jam into warm, dry jars. Cover.