Slice the plums in half and remove the seed.
Cut the halves into 4 and add to the blender, no need to remove the peeling.
Add all the other ingredients to the high speed blender and blend until smooth.
If the mixture is too thick, add water, about 1 to 2 Tbsp. at a time until desired thickness.
Note: Keep in mind that you will be cooking the sauce to reduce.
Pour the mixture into a medium sized sauce pan.
Cook at a medium heat for about 10 to 15 minutes, or until thick like a BBQ sauce.
Remove from heat to let cool.
Once cool, store in a canning jar, and place into the refrigerator until ready to use.