Our Blackberry Jam is mostly sweet, with a touch of acid, and we’ve left the seeds in so you get a little texture and crunch. You’ll get the most accurate results with a thermometer, but we’ve provided an alternate method for those who prefer to go without. What’s crucial here is not to overcook the jam: Once you’ve hit the 15-minute mark, turn off the heat and test to see if your jam has set. Then, continue to test in 5-minute increments until it’s set, otherwise the flavor will be…