1 tablespoon grated blood orange zest
3/4 cup sugar
3 cups fresh blood orange juice
1/4 cup fresh lemon juice
Mash the blood orange zest with one teaspoon of the sugar to release its oil. Stir the remaining sugar into the blood orange juice and let it stand until dissolved; Stir in the zest and the lemon juice. Refrigerate until thoroughly chilled, about 2 hours.
Freeze the mixture in an ice cream maker according to the manufacturer’s instructions. Or, to freeze without the ice cream maker, pour the mixture into an 8- or 9-inch metal pan or a half-gallon plastic container. Cover and freeze until firm, about three hours. Transfer to an electric mixer or food processor and beat until light and fluffy. Transfer to a container, cover, and freeze until firm, about 1 to 2 hours.
Serve garnished with mint leaves.