Put a liner on top of the grill tray in your air fryer. If you don’t have one, cut a piece of greaseproof paper to about the same size as the base of your tray. Fold it in half 3-4 times to create a thin triangle. Make holes with a skewer or hole punch and unfold.

Put the sugar, flour and cold, cubed butter in a bowl and rub together until you have an even crumb.

Add 1 1/2 tsp of cold water and cut through with a cutlery knife. Give a little bit of the mixture a squeeze. If it comes together, it’s ready. If it’s dry and sandy, cut in up to another 1 tbsp water.

Gather and knead the mixture just enough to bring it together as a smooth dough. Be careful not to overwork it.

Gently shape the dough into a rectangular length - about 10cm long x 2.5 cm tall x 5cm wide (4 inches long x 1 inch tall x 2 inches wide). Wrap in cling film and place in the freezer for 15 minutes.

Once the dough is very firm, unwrap and cut into 1 cm (1/2 inch) cookies. Prick each one all over with a fork.

Place the cookies in the air fryer basket, with about 2cm / ¾ inch between them.

Set air fryer to 130C fan / 265F and bake for 20-25 minutes until they've taken on just a very slight golden colour.

As soon as they’re out of the air fryer, sprinkle with the remaining sugar and allow to cool for 5 minutes, then transfer to a wire rack to cool completely.