Pour the water, sugar and lemon zest into a pot over medium high heat until the sugar has completely dissolved, stirring occasionally.
Remove from heat, stir in the mint and set aside.
As the simple syrup steeps, whisk together the lemon juice, limoncello and salt.
Pour into the minted simple syrup and allow to cool completely. Chill for at least 3 hours, but preferably overnight.
Once the liquid has chilled, pour it into the frozen base of your ice cream maker, cover with the lid and churn for 20-30 minutes or until the mixture thickens.
Put the base into the freezer for another hour or two to harden as desired.
