Finely chop the pistachio nuts and save the dust. Pound the dust to a smooth paste with a little water and green colour to moisten.
Add this paste to the yolks and whisk until thick and an even pale green, about 5 minutes.
Meanwhile bring to the boil the sugar and the water. While still bubbling, trickle onto the yolks and whisk at a high speed until thickened and cold. Place in the freezer.
Whisk the cream, Chartreuse and icing sugar until thick. When the egg mixture starts to set, fold in the whipped cream and chopped pistachios. Freeze.
© 1984 All rights reserved. Published by Jon Croft.