Combine first 4 ingredients in a medium, heavy saucepan; stir with a whisk. Gradually add low-fat milk and evaporated milk, stirring with a whisk. Bring to a boil over medium-high heat, stirring constantly with a whisk. Reduce heat, and simmer 1 minute or until thick. Remove from heat; add chocolate, stirring until melted and mixture is smooth. Stir in vanilla. Pour about 2/3 cup pudding into each of 6 (8-ounce) ramekins; cover surface of each serving with plastic wrap. Chill at least 4 hours. Remove plastic wrap; serve. Garnish with fresh mint sprigs, if desired.