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

Chop the chocolate finely. Place ⅔ of it into a small heatproof bowl and melt in the microwave I do this by heating in 30 second bursts on full power, stirring occasionally. Once the chocolate has almost melted I add the remaining ⅓ chocolate and stir until it is all completely melted

Take a biscuit and dip the bottom ⅓ in the chocolate, tilting the biscuit as necessary to ensure a good covering of chocolate. Place on greaseproof paper. Repeat with another 2 biscuits. Top each biscuit with a small pinch of sea salt flakes (don't wait until you have dipped all 20 biscuits - the chocolate will have set too hard for the salt to stick)

Keep repeating this dipping and sprinkling process with sets of 3 biscuits until all of the biscuits have been decorated

Allow to set completely then transfer to an airtight container. Keeps for up to 5 days