Line a baking sheet with parchment paper. Spread the nuts out in a single layer and toast in the oven for 8 minutes. Cool. Heat the milk and cream together in a saucepan until scalding. Grind the cooled nuts in a food processor until fine but with a little texture, if you like texture. Add the vanilla and salt, and stir well.
Whisk the sugar and eggs together until thick and creamy, and the whisk leaves a trail when lifted from the bowl, approximately 8–10 minutes.
Combine the milk and eggs together in the pan and gently cook the custard mixture over low heat. This should not take longer than 8 minutes. Stir really well as this could turn to scrambled egg, so heat gently and carefully.
If you would like a pronounced green gelato, cool the mixture and leave overnight in the fridge, then freeze and churn in an ice-cream machine as per the manufacturer’s instructions. If, like me, you are impatient, leave the creamy pistachio custard to cool, then freeze and churn.
Serve on its own, or with chocolate ice cream – they are rather good together.