Oriental Plum Sauce

10 cups prepared plums
2 cups packed brown sugar
1 cup granulated sugar
1 cup cider vinegar
3/4 cup finely chopped onion
2 T. mustard seed
2 T. finely chopped green chili peppers
1 T. salt
1 to 2 cloves garlic, minced
1 to 2 pieces (each 1/4 x 1 inch) gingerroot, minced

Combine all ingredients expect plums in a large stainless steel or enamel saucepan. Bring to boil; add plums. Return mixture to boil; boil gently, stirring occasionally, about 1 3/4 hours or until thick and syrupy.

Fill jars leaving 1/4 inch headspace. Seal and process in a hot water bath for 10 minutes.