Tie cinnamon, allspice, and cloves in spice bag or cheesecloth. In a crockpot, combine spice bag, apple juice, rum and brown sugar. Cover; cook on low-heat setting for 3 to 4 hours. Discard spice bag. Ladle hot punch into cups; float about half teaspoon of butter on top of the cider in each cup.
Yield: 10 servings of 6 ounces each.