Begin by blitzing 50g of the pistachio nuts in a processor or coffee grinder until reduced to a fine powder (similar in appearance to ground almonds, only green!)
Chop the remaining 25g of nuts using a knife
In a medium bowl, using electric beaters, cream the butter with the sugars until fluffy
Add the cooking salt, flour, ground and chopped pistachios. Briefly stir with a metal spoon, then use your hands to complete the mixing. Stop mixing as soon as everything is combined properly
Roll the dough into a cylinder (sausage) approximately 20cm long and 4-5cm wide. Wrap in clingfilm and chill for at least 4 hours
Pre-heat the oven to 140°C/ 275°F/ GM1 and line 2 baking sheets with baking parchment
Unwrap the dough, slice the ends off to neaten and then gently slice the cylinder into 20 rounds about 5mm thick.
Lay the circles on the baking sheets, spaced 2cm apart. (Take care to pick the side that has the prettiest display of nuts and put this face up).
Bake for around 20 minutes until beginning to turn golden. Remove from the oven, let rest for 2 minutes before transferring to a wire rack to cool completely