Combine whipping cream and butter in heavy saucepan; cook over low heat, stirring constantly, until butter melts. Bring mixture to boil. Remove from heat; add chocolate, stirring until chocolate melts. Stir until mixture thickens. Stir in liqueur flavoring. Cover and chill 3 to 4 hours, stirring frequently. Shape mixture into 1-inch balls; roll lightly in cocoa. Yield: about 3 1/2 dozen.