- 1 small onion, finely chopped
- 1 tablespoon vegetable oil
- 1 pound black plums (4), pitted and coarsely chopped
- 1 1/4 cups water
- 1/4 cup plum jam
- 2 teaspoons balsamic vinegar
- 2 teaspoons Dijon mustard
- 1/4 teaspoon black pepper
- 1/4 teaspoon salt
- Cook onion in oil in a 3- to 4-quart heavy saucepan over moderate heat, stirring occasionally, until golden, about 5 minutes. Stir in remaining ingredients and simmer, uncovered, stirring more frequently toward end of cooking, until plums fall apart and sauce is thickened, about 1 hour. Cool to room temperature. Serve with pork or chicken.