Bring first 4 ingredients to a boil in a Dutch oven over medium-high heat, stirring occasionally; reduce heat to low, and simmer, stirring occasionally, 20 minutes or until mixture thickens. Pour through a fine wire-mesh strainer into a large bowl, discarding solids. Clean Dutch oven. Return plum mixture to Dutch oven.
Bring to a boil over medium heat; add sugar, and simmer, stirring often, 10 minutes or until slightly thickened. Let stand 15 minutes. Use immediately, or refrigerate in an airtight container up to 3 weeks.