How to Make It
Combine rice vinegar and next five ingredients in a stockpot. Bring to a boil over high; reduce heat to medium, and simmer 5 minutes.
Divide and pack plum quarters evenly into 8 (1-pint) canning jars. Add 1 piece star anise and 1 cinnamon stick half to each jar. Carefully ladle hot vinegar mixture over plums in jars, leaving 1/2 inch of room at the top of each. Wipe rims. Cover at once with lids; screw on bands. Let stand 2 hours. Chill 1 week before serving. Plums will keep up to 2 months in refrigerator.
Total time includes 1 week chilling