5 lb. Red Plums
a large bunch of fresh Thyme
½ c. sugar
1½ c-2 c. sugar
5½t. low-sugar pectin
calcium water (prepare as directed on pectin package)
2 qts. jam
(I've also attached a printer-friendly pdf of the complete recipe.)
Step 1: Roast Fruit
Preheat your oven to 425°F. Halve the plums and place them pit side up on a baking sheet. (If the pits are difficult to remove, you can remove them later). Tuck sprigs of thyme into the fruit and sprinkle with ¼c. sugar. Roast for 25 minutes, until the fruit is soft and just lightly caramelized. Leave out until the fruit is cool enough to handle.
While the fruit is in the oven, you can sterilize your jars. Wash and rinse the jars and lids you’ll be preserving in. Place the jars in a stock pot with a small grate on the bottom. Pour hot water from the tap over the jars and let them sit for a few minutes to slowly warm up. Place the stockpot over high heat. Cover and bring to a boil. Turn heat off and leave jars to sit in the hot water.
Step 2: Prepare Fruit
Scoop pits out of plums and discard. Separate the plums from the skins, placing the skins, thyme and the plum syrup in a saucepan and the fruit in a separate bowl or stock pot. The plum flesh will have turned a beautiful ruby color. You should have about 5c. of plum flesh and 4 c. of combined juice and skin.
Zest the two lemons. Add the lemon zest to the saucepan with the plum skins and juice. You can taste the juice and decide if you want a more pronounced thyme flavor. If you do, then add in a few thyme sprigs to the saucepan as well. Bring to a boil. Let mixture boil down to 2 c. Stir frequently to prevent sticking on the bottom of the pot. Strain and add to the reserved plum flesh.
Place jam in a large stockpot. Juice lemons. Add lemon juice and 1c. sugar to the jam and place over high heat. Add calcium water. Mix pectin with ½c. sugar. Once the jam has come to a boil, slowly stir in the pectin to the jam mixture until it is thoroughly dissolved.
Remove jars from the hot water and place on a clean dishcloth. Fill with hot jam to ½” from the top of the jar. Place jars on lids and tighten. Place filled jars back in the stockpot and fill with hot water. Bring the stockpot to a boil and process jars for a full ten minutes. Carefully remove jars and set on a clean dishcloth to dry. Once the jars have cooled check to see that they have fully sealed.
Sealed jars will keep for a year or more. Once the jar has been opened it will keep, refrigerated, for three weeks.