Juice the lemons until you reach one cup of lemon juice. Strain to remove seeds and pulp.

Finely chop fresh basil leaves using the chiffonade technique.

Combine water and granulated sugar in a saucepan. Stir over medium heat until sugar dissolves, about 3-5 minutes.

Stir in fresh lemon juice and chopped basil once sugar syrup cools.

Chill mixture in the refrigerator for at least four hours.

Churn the mixture in an ice cream maker according to directions until it reaches a soft-serve consistency.

Transfer to an airtight container and freeze for a few hours to firm up.