Heat sugar and water in a saucepan, stirring occasionally until sugar dissolves. Bring to the boil over a medium heat, add berries and cook for a couple of minutes until soft.

Using a potato masher, roughly mash up berries.

Remove from the heat, add the mint leaves and allow to cool completely.

Strain the mixture through a sieve to remove all the berry seeds and pour into a plastic container. Freeze overnight.