In heavy kettle stir plums and 1/2 cup sugar over lowest heat. When juices flow, bring to boil; cook 5 minutes or until fruit is tender. Pour into blender. Chop on low speed, 2 seconds. Return to kettle; add remaining sugar and spices. Bring to boil.
Reduce heat, yet maintain active bubbling; cook 5-10 minutes, stirring frequently. Test for doneness -- mixture "sheets" from spoon, or pour teaspoonful on chilled sauce -- if no rim of liquid forms around edge of butter it is done. Ladle at once into hot sterilized screw top jars leaving 1/2 inch headspace. Seal with clean, dry, metal lids. Makes 3 1/2 pints.