Gently toast the pistachios in a heavy bottomed frying pan until they smell nutty; allow to cool a little then finely chop them.

Put the chopped pistachios in a saucepan with the milk and sugar, heat until almost simmering and the sugar has dissolved then remove from the heat and use a stick blender to blitz the mixture until it is completely smooth.

Add the cream and salt and return the pan to the heat; mix the cornflour with the 2tbsp of milk to make a slurry and whisk it into the pistachio cream. Whisk constantly until the mixture has thickened and come up to the boil, continue to cook for another minute or so, while whisking, to cook out the cornflour.

Pour into a bowl, cover and allow to cool, refrigerate until completely cold. If you like you can whisk in a couple of drops of green food colouring to accentuate the pistachio's colour; don't add so much that it looks fake though!

Churn in an ice cream machine according to the manufacturers instructions. About five minutes before the ice cream is finished churning, melt the chocolate and pour it into a ziplock bag or disposable piping bag; snip off the tiniest corner of the bag and drizzle the chocolate in a thin stream onto the churning ice cream, as it hits the cold ice cream it will solidify and break into small shards. Try to avoid pouring the chocolate onto the beaters.

Scrape the ice cream into a container and freeze for a couple of hours until firm before serving.