Spiced rum is the secret to this delicious drink because it adds depth and flavor with just one ingredient. If you really want a stand-out cocktail, it's easy to make your own spiced rum. Simply combine a bottle of rum with whole spices such as cloves, cinnamon sticks, allspice berries, black peppercorns, and star anise (fresh ginger is also a great addition). Store it in a large jar with a tight-fitting lid and let steep for a few days, shaking daily. When the flavor is to your liking, strain and bottle it, then put it to use in cocktails such as this one.