tesco.com has a very simple recipe and the jam has a lovely autumny/wintery spice taste to it.
900g stoned and chopped plums
900g granulated sugar
1 tsp ground cinnamon
1 tsp ground ginger
1 tsp butter (to clarify)
Place a saucer in the freezer.
Put the stoned and chopped plums in a wide stainless steel pan or preserving pan with 150ml water. Bring to the boil and simmer for 20-30 minutes until the fruit is soft. As I had frozen my plums, they were soft enough to skip this step.
Wash and sterilise your jars and lids as soon as the jam goes on. I reuse the ‘pop up’ style lids as these help seal the jam and allow you to keep it in a dark place for 1+ years. Wash jars and lids in hot soapy water, rinse well and drain. Place the jars in a cold oven, let it heat up to 140C and then leave for 10 minutes at this heat or until your ready to pot up. Place the lids in a pan with boiling water and boil for 10 minutes to sterilise.
Add the sugar and stir over a low heat until all the sugar has dissolved. Stir in the cinnamon and ginger and bring to a rolling boil. Boil rapidly for 10 minutes without stirring. With a spoon, pour a little onto the chilled saucer. After a few seconds push the jam with your finger. If it wrinkles, it is ready. If not, return to the boil for another 5 minutes and test again, stirring from time to time. It took about 20 minutes when I made this jam this afternoon, and I did have to stir it to stop it catching on the bottom of the pan especially towards the end of cooking.
When ready remove from the heat. Stir in the butter which should make any scum ‘vanish’. Take your jars out of the oven and fill right to the brim. Seal immediately with your sterilised lids and leave to cool.