Method

• 1.
  Zest lemons and oranges and place zest in saucepan with the sugar and 600ml water. Cook over a medium heat for 5 minutes, stirring to dissolve the sugar. Bring to the boil and boil for 5 minutes. Strain and set aside to cool.
• 2.
  Juice the lemons and oranges (you will need about 600ml of juice) and add this to the cooled syrup. Tear the basil leaves into the mixture and pour into a food processor. Process until just combined (don't over-process, you need to be able to see the basil). Transfer the mixture to a freezer-proof container and freeze for 2 hours until ice crystals have started to form around the edges. Beat with a fork then return to the freezer. Repeat this step 2 more times. (Alternatively use an ice-cream maker and churn following manufacturer's directions.)
• 3.
  Serve in small glasses as a palate refresher or pour over a little gin for a cool aperitif.