Place all ingredients in a medium-sized pot. Set over medium heat and bring mixture to a gentle simmer (sauce should just gently bubble). Cook 20 to 25 minutes, or just until the cranberries soften and slightly fall apart. Cool sauce to room temperature. Store sauce in a tight sealing jar in the refrigerator until needed. Sauce can be made several days before needed.
Recipe Options: Instead of regular port, try a flavoured port in this sauce, sauce as the blackberry port sold at some liquor stores and wineries in British Columbia. Instead of currants, use raisins in this recipe.