You may remember our last attempt at this jam, when it turned out a wee bit hard. But because the flavor was so good, and because we were determined not to let the jam win, we gave it another try...
This time, we made a couple of changes. We peeled the peaches, making the jam a little paler than our last batch. And instead of using the plate-in-the-freezer trick to determine when the jam was finished cooking (apparently a nuanced technique that we have not mastered), we relied on a candy thermometer. We'd read 220 degrees was a good target, so we set off boiling the jam and watching the thermometer.
The thing is, that method wasn't foolproof, either. We boiled and stirred and watched the temperature hover at 200 degrees. About 20 minutes passed, and we started to have flashbacks. Bubbles were splattering, sugar was starting to sizzle quietly on the bottom of the pot as we scraped. We stuck a second candy thermometer in the pot, fearing the first was broken, but it, too, stayed steady at 210 degrees.
Then, we panicked. We turned off the heat and called it an afternoon. Now that the jam has cooled, it's perfectly lovely. Maybe a little on the thin side, but certainly spreadable and preferable to the alternative. So, our advice is: Shoot for 220 degrees. Don't worry if you panic.
Cut the plums away from their pits and into chunks. Pit and peel the peaches and cut into chunks. You should have about four cups of fruit. Add fruit and the rest of the ingredients to a large sauce pan.
Heat the mixture over medium-high heat until it comes to a boil. Continue to boil, stirring constantly, mashing the fruit into small pieces as it softens and cooks. (We actually got a potato masher in there at one point, since our chunks were too big.) Cook until a candy thermometer reaches 220 degrees, about 20 to 25 minutes.
Remove from heat, cool, and store in an airtight container in the refrigerator.
*This happened to be what we had. You could certainly try this recipe with other kinds of plums or even all peaches.