Though optional, crème de menthe adds a second level of mint flavor, softens the texture, and lends the ice cream a pretty, pale-green color.
Prepare Vanilla Ice Cream, omitting the vanilla or vanilla bean. Bring the cream or milk mixture to a simmer as directed and stir in 1 cup chopped mint. Remove the pan from the heat, cover, and let steep for 30 minutes. Strain the mixture into a medium bowl, pressing firmly to extract all the liquid; discard the mint. Proceed as directed. If desired, add (1 to 2 tablespoons crème de menthe) just before refrigerating the ice cream base. When the ice cream is almost frozen, stir in 3 to 4 ounces semisweet or bittersweet chocolate, chopped.