In a large bowl, combine the self-raising flour, caster sugar, baking powder, and a pinch of salt.

Add the chilled, cubed butter to the bowl. Rub the butter into the flour mixture using your fingertips until it resembles fine breadcrumbs.

If using, add the currants or sultanas and mix well.

Make a well in the centre of the mixture. Pour in the milk and mix it quickly with a round-bladed knife to form a soft dough. It will be quite soft and sticky.

Dust a surface with flour and turn out the dough onto it. Knead it very briefly and gently until it's just smooth. Be careful not to over-knead.

Roll out the dough until it's about 3 or 4 cm thick. Use a round cutter to cut out the scones from the dough. I managed to get around 6 scones out of this mixture.

Arrange the scones in the air fryer basket, making sure there's space between them for the scones to expand as they cook. You might have to cook in batches depending on the size of your air fryer.

Brush the tops of the scones with milk.

Air fry the scones at 180°C for about 10 minutes or until they are well-risen and golden brown.