Grind the pistachio and 50 grams of sugar in a food processor.

Add the milk to a pan, mix in the ground pistachio, and bring it to a boil. Do not boil it though — remove from heat as soon as the mixture reaches the boiling pint.

Separate the egg yolks and mix them with the rest of the sugar in a bowl.

Add the hot mixture to the bowl gradually, whisking continuously.

Return the custard to the pan and cook over low heat until it thickens, but be careful not to boil it. It should have the consistency of a thick custard.

Remove the custard from the heat, transfer to a bowl, and let it chill completely (2 or 3 hours).

Whisk the double cream and add it to the custard.

Churn the mixture into an ice cream maker according to the instructions of the manufacturer.

Transfer to a container and freeze until firm.