Damson Plum Cardamom Jam

Step 1
Rinse and de-stem plums in a sink full of cool water; place them into a thick-bottomed pot suitable for slow cooking and deep enough to allow frothing when plums begin to boil. Add water and cardamom pods; bring to a low boil over medium heat. Turn heat to low for a slow simmer and allow plums to cook down uncovered for 1 hour and 30 minutes. Remove from heat and allow to cool.

Step 2
Strain cooled plums in a colander set over a large bowl. Press juice out with your hands, collecting it in the bowl. Pick up small handfuls of the pit-and-fruit slurry in the colander and squeeze pulp and skins gently into the bowl with the syrup, retaining the pits in the palm of your hand and then discarding them.

Step 3
Place plums back into the pot. Add sugar and butter; mix well. Cook at a very low simmer until jam thickens, about 4 hours. Test for adequate development of pectin by dropping a spoonful of jam onto a plate and putting it in the refrigerator for a few minutes: jam should be soft-set and no longer syrupy.

Step 4
Ladle jam into hot, sterilized jars, filling to within 1/4 inch of the top. Run a clean knife or thin spatula around the insides of the jars to remove any air bubbles. Wipe rims with a moist paper towel to remove any residue. Top with the lids and screw the rings on tightly. Allow the jars to cool to room temperature and check to be sure that each jar has sealed.