4 pounds Italian prune plums
2 cups sugar
1 cinnamon stick
2 whole cloves
- Pit and quarter the plums and put them in a heavy 4-quart pot. Add the sugar, the cinnamon stick, and the cloves. Stir well and let sit overnight or for 8 hours.
- The next day, heat the oven to 350 degrees. Put the pot, un-lidded, into the oven and cook for 2 hours, stirring the mixture occasionally.
- Sterilize the glass jars in boiling water for 10 minutes.
- When the plums have broken down and the liquid has reduced to a thick jam, remove pot from the oven and fish out the cinnamon stick (if you can find the cloves, fish them out too).
- Puree the jam with an immersion blender until it resembles a fruit butter, and then fill the sterilized jars with the hot puree, screw on tops and process in a boiling waterbath for 10 minutes. If you prefer a jam with discernible chunks of fruit, however, don't puree the jam; simply ladle the hot jam into the sterilized jars.