Rinse the fruit. You want to start with really clean fruit because in this recipe we won’t be removing the skins -hallelujah! The skins mostly kind of dissolve during the cooking process and are unnoticeable in the final product. One less step for us and more vitamins and nutritional value in the jam!
Prep the fruit. Using a paring knife, remove the cheeks of the plum and then cut off the top and bottom. Make sure to pare away any bruises or other blemishes on the fruit. Cut the fruit into small pieces so they will cook down faster. Stir frequently.
Cook the fruit. Throw all of the fruit into a heavy-bottomed pot and start cooking. Add in the lemon juice now. For every 1 1/3 cups of prepared fruit, you need to add 3 tsp of bottled lemon juice. I let my fruit cook down for 10-15 minutes before adding in the pectin. Stir frequently.
Add in the pectin and butter. Bring to a full rolling boil that cannot be stirred down over high heat. Stir constantly.
Add the sugar. Stir to dissolve and return the mixture to a full rolling boil.
Boil hard for EXACTLY ONE MINUTE stirring constantly and then remove from heat.
Skim foam. I didn’t have a lot of foam but I noticed that what skins hadn’t dissolved were hanging out with the foam and they got tossed too.
Prepare the waterbath canner, jars and lids. This should be done while the jam is being made. I boiled all components to make sure they were sanitized completely. I know many people run them through the dishwasher and that’s fine too.
Ladle the hot jam into the hot jars using a funnel. Trust me. Funnels keep the mess to a minimum and keep you from getting burned. Handle all jars with care because they are HOT. Leave 1/4 inch headspace and wipe the rims of the jars. Place the lids on the jars and finger tighten the bands.
Next it’s time to place the jars in the canner. The jars need to be covered by at least 1-2 inches of water. Place the lid on the canner and bring water to a boil. Process the jars for 10 minutes and then turn off the heat. Let jars stand for 5 minutes before removing.
Let the jars cool for 24 hours. Check the lids for a proper seal by pressing on the center. The lid should not flex at all. Loosen the band to prevent any moisture from being trapped and store. You’ve just jammed!