Salted pistachio and lime ice cream

Method

1. Whizz the pistachios until very fine in a food processor (but be careful not to overmix, as they may start to release their oils), then tip into a medium saucepan with the milk, cream, lime zest and juice. Heat gently, stirring often, until steaming hot, then remove from the heat.
2. Meanwhile, in a separate bowl, use a balloon whisk to mix the egg yolks and sugar for 1 minute until thoroughly combined.
3. Half-fill the sink with cold water. Gradually whisk the hot cream into the yolk mixture, whisking continuously to form a custard. Return the custard to the pan and cook over a low heat, stirring all the time, until it reaches 82°C on a sugar thermometer (or becomes thick enough to coat the back of a spoon). Don’t let the custard boil or it will scramble. As soon as it reaches the right temperature or thickens enough, plunge the base of the pan into the sink of water to cool. Speed up the cooling process by stirring the mixture every so often. Once the custard is at room temperature, pour the mixture into a clean container and stir in the sea salt flakes. Cover the surface with baking paper, put the lid on and chill overnight.
4. The next day, pour the custard into an ice cream machine and churn for 25-45 minutes (depending on your machine) until it reaches the texture of thick whipped cream. Transfer to a lidded container, seal and freeze for at least 4 hours until ready to serve. It will keep for up to 3 months in the freezer. Soften for 5-10 minutes out of the freezer before serving (see serving tip).