Sterilize all of your mason jars in your combi oven for 10 minutes at 225F (107C).
Remove sterilized mason jars from combi oven.
Wash the plums thoroughly.
Steam the plums for 8 min at 212F (100C).
Use a paring knife to peel the skin from the plums and remove pit.
Ready to cook.
Cook plums until soft
Mix sugar and fruit pectin
Stir pectin sugar mixture into fruit.
Fill Jars with the warm fruit mixture
Cover with two-piece lids. Screw bands tightly.
Steam in combi at 190F (88C) for 10 min. This will pull the vacuum.