In a small saucepan, heat the milk and 30g of pistachios. Turn off the heat just before it begins to simmer. Allow to cool

Put the double cream, condensed milk, vodka and puréed pistachios into an electric mixer fitted with the whisk attachment. Beat on a high speed until firm (about 2 minutes)

Decant the mixture into a 1-litre lidded tub/container, sprinkle the chopped pistachios over the top and freeze for at least 4 hours - preferably overnight.