Combine juice with honey and vanilla in a medium saucepan. Bring to a boil. Reduce heat and simmer for 5 min.
Stir in plums. Simmer, covered, for 5 min.; remove lid and simmer 10 min. longer or until plums are fork-tender but still intact. Cool slightly or chill before serving, garnish with mint. Keep any leftovers in a covered container in the refrigerator for up to 3 days.