In a medium saucepan, combine the honey and water and bring to a boil.
Bring a canning pot or large stock pot to a boil. Put your lids into a small saucepan and bring to a simmer.
Clean canning jars and pack the plums in as tightly as you can. Insert your cinnamon stick, vanilla bean or star anise. Fill jars with honey syrup, leaving 1/2 inch of headspace.
Wipe rims to remove all traces of any spilled honey syrup, apply lids and tightened rings. Process in a boiling water canner for 25 minutes (starting time when the pot returns to a boil after the jars have been placed inside).
When processing time is up, remove the jars to a cutting board or towel-lined countertop (as they cool and seal, they might spit out a bit of sticky syrup, so don’t let them cool on any surface that can’t handle that). Let the jars cool undisturbed for 24 hours.
When jars are completely cool, remove the rings, check the seals and wipe the jars down to remove any sticky residue. Label and store in a cool, dark place for up to a year.