Courtesy: Beth Knorr (adapted from this blog)
5 lbs plums, preferably Stanley or Damson, pitted and roughly chopped
2 cups sugar
4-5 star anise blossoms
Place plums, star anise and sugar in a non-reactive saucepan and let sit in refrigerator for several hours or overnight until juices begin to form a thick syrup. If you are pressed for time, you can skip this step.
Bring plums to a simmer, and cook until they have broken down, and the juices pour off a spoon in a sheet, roughly 40 minutes to an hour. Check flavor from time to time during cooking process and remove star anise blossoms when the flavor imparted is the strength you like.
Meanwhile, sterilize jars by boiling in your canning pot for 10 minutes. Pour hot water over jar lids to soften rubber ring.
Once jam reaches desired consistency, pour into sterilized jars, put on lids and tighten bands just to finger-tight, and bring water back to a boil.
Once the water is boiling, process for 10 minutes. Remove from canning pot and set on a clean towel away from drafts. Listen for the "ping". If it does not ping, refrigerate and consume immediately, or re-process.
Makes roughly 3 pints.