Place all of the ingredients in a medium saucepan and bring to a boil over medium heat.

Reduce heat and simmer for 25 minutes or until the plums are soft and the sauce has thickened slightly.

Remove from heat and pour the sauce into a food processor or blender. Puree until smooth and return to pot. (Alternately, you can use an immersion blender right in the pot. Be careful blending hot liquids!).

Bring the plum sauce back to a boil, then ladle into hot, sterilized jars, leaving 1/4 inch headspace.

Place sterilized lids and rings on the jars and process for 15 minutes in a boiling water bath.

Remove jars to a towel to rest for 24 hours. Check seals before storing.