Method Prep:10min › Extra time:3hr freezing › Ready in:3hr10min
Combine the lemon zest and sugar in the container of food processor. Process until the zest is fine.
In a medium bowl, stir together the sugar mixture and milk until sugar has dissolved, then stir lemon juice. In a separate bowl, whip the double cream until stiff but not grainy. Gently fold the whipped cream into the lemon mixture until blended.
Pour the mixture into a bowl or container, then cover with cling film or a lid. Freeze it for at least 3 hours.