01 - Slice 1/4 inch from the stem end of each kiwi. Using a spoon, gently scoop out the flesh, keeping the skins intact. Place shells upright on a tray and freeze until firm.
02 - Combine scooped kiwi flesh, lemon juice, granulated sugar, and mint leaves in a blender. Blend until the mixture is completely smooth.
03 - Chill the purée, then churn in an ice cream maker for 20 to 25 minutes until thick. If an ice cream maker is unavailable, spread the mixture in a shallow freezer-safe dish and stir with a fork every 30 minutes for 2 to 3 hours.
04 - Spoon the sorbet into the frozen kiwi shells. Level the tops and return the filled shells to the freezer for an additional 2 to 3 hours until firm.
05 - Garnish each sorbet shell with fresh mint sprigs or thin kiwi slices as desired. Serve frozen in egg cups or small glasses for stability.