Heat oil in a medium saucepan over medium heat. Add onion; cook 3 minutes or until tender, stirring frequently. Stir in broth, blueberries, vinegar, molasses, 1/4 teaspoon salt, 1/4 teaspoon pepper, coriander, and plums; bring to a boil. Reduce heat, and simmer 20 minutes or until plums are tender and mixture is thick.