True chocolate-lovers will want to use bittersweet chocolate, which carries a more pronounced flavor than semisweet in this warming beverage.
In a small saucepan combine water and chocolate; cook and stir just until boiling. Remove from heat; stir in liqueur or vanilla. In a small chilled mixing bowl beat cream with an electric mixer on low to medium speed until soft peaks form (tips curl). Top each serving of cocoa with whipped cream; sprinkle with orange peel, if desired. Makes 4 (4-ounce) servings.