Cook first 5 ingredients in a heavy saucepan over low heat, stirring until smooth. Cool.
Fold chocolate mixture into whipped cream. Spoon mousse into a plastic wrap-lined 9- x 5-inch loafpan. Freeze 8 hours.
Invert onto a plate; remove plastic wrap. Decorate with ribbon and a rose to resemble a wrapped package. Store in refrigerator; serve with additional whipped cream, if desired.
