Bake ribs in the oven at 350ºF (180ºC) for 1½ hours. Drain oil and return ribs to roasting pan.
In a saucepan, mix together brown sugar, barbecue sauce, dry mustard, cinnamon, ketchup, soya sauce, garlic and pepper. Heat until almost boiling.
Add cornstarch to rum to thicken, then add to saucepan mixture. Heat thoroughly until thickened and almost boiling. Pour mixture over ribs, cover, and return to oven for another 1½ hours, but at 250ºF (120ºC). Makes 4 to 6 servings.