Combine the water and sugar in a small saucepan. Heat and stir until sugar is dissolved. Remove from heat. Add the 1-1/2 cups mint leaves. Cover and let stand for 10 minutes. Strain into a large mixing bowl; discard mint. Stir the concentrate and lemon peel into strained mixture; refrigerate 1 to 2 hours or until chilled.
Freeze in a 2-quart ice cream freezer according to manufacturer's directions. Ripen for 4 hours. (Or, transfer mixture to a nonmetal freezer container. Cover and freeze for 4 to 6 hours or until almost firm. Break mixture into small chunks; transfer to a chilled bowl. Beat with an electric mixer until smooth but not melted. Return to container. Cover and freeze for 6 hours or until firm.)
To serve, scoop mixture into individual dessert dishes. If desired, garnish with mint leaves and blossoms. Makes about 4 cups or 8 servings.