by Rachel Saunders of The Blue Chair Jam Cookbook
(makes about eight 8-oz jars)
5 lbs pitted and halved plums 1/2 cup + about 1/2 - 2/3 cup strained freshly squeezed lemon juice (you’ll use lemon juice in two different steps) 2 1/2 lbs cane sugar
MACERATE: Place the plums in a large non-reactive container. Pour ½ cup lemon juice over the fruit and stir to combine. Then pour the sugar evenly over the fruit. Do not stir. Press a sheet of plastic wrap directly onto the surface of the mixture to keep the fruit from browning. Cover tightly with a lid and place in the refrigerator to macerate for 2-7 days (or longer - up to several weeks), stirring every couple days.
TASTE: Remove plums from fridge and stir in 1/2 cup lemon juice. Taste for lemon flavor. If you do not detect any lemon, slowly add a little more, stirring and tasting as you go, until you can taste the tartness and lemon flavor.
COOK: Transfer the mixture to a wide-bottomed pot like a Dutch oven or jam pan. Bring the mixture to a boil over high heat, stirring occasionally. Cook, stirring frequently, for 4 minutes. Remove from heat. Skim and discard foam. Return to a boil, then decrease the heat slightly.
Continue to cook until the jam thickens (about 30 -40 minutes). Scrape the bottom of the pan often with your spatula, and decrease the heat gradually as more moisture cooks out of the jam. For the last 10-15 minutes of cooking, stir the jam slowly and frequently to keep it from scorching.
Test for doneness using the Freezer Test. Once a “set” is achieved, turn off the heat and do not stir. Skim any foam from the surface. Pour the jam into sterilized jars using a canning funnel and process by water bath canning, oven canning, or refrigerate.