In a bowl, use your thumbs and fingertips to rub together the soft butter, flour, sugar and a pinch of sea salt, then finely chop and add the ginger.Squash and pat into a dough, shape into a large log, wrap in greaseproof paper and twist the ends to seal. Firm up in the fridge for at least 20 minutes.Once firm, slice the log into 12 even-sized rounds. At this point, you can bake however many biscuits you like, working in batches, if necessary, and simply freeze the rest to cook another day – wrap the biscuits in greaseproof to prevent them sticking together.To cook, line the air-fryer drawer with a sheet of greaseproof, evenly space however many biscuits you want on top, then bake for 14 minutes at 170°C (17 minutes from frozen), or until golden. Remove to a wire rack, sprinkle with a little extra sugar, if you like, then leave to cool completely.Snap the chocolate into a heatproof bowl and melt in the air fryer for 2 minutes at 170°C, stir until smooth, then drizzle over the cooled shortbread.This recipe is for a 1-drawer air fryer.