1.In a large saucepan, combine all ingredients, except star anise, cassia bark (or cinnamon stick) and sugar; bring to the boil.
2.Reduce heat; simmer, uncovered, stirring occasionally, about 15 minutes or until mixture is pulpy. Strain mixture through a fine sieve into large bowl; discard solids.
3.Return plum mixture to pan with sugar and sauce. Tie cassia bark (or cinnamon stick) and star anise in muslin; add to pan. Stir over high heat, without boiling, until sugar dissolves.
4.Reduce heat; simmer, stirring occasionally, about 1½ hours or until sauce is thick. Discard muslin bag.
5.Spoon hot sauce into hot sterilised jars; seal immediately. Label and date jars when cold.
Store in a cool, dark place for one week before opening. Sauce will keep in a cool, dark place for up to six months; refrigerate after opening. It will keep for many months in the refrigerator.Note