Put the flour into a bowl with a pinch of sea salt, then chop and add the butter, rubbing it in with your thumbs and fingertips. Make a well in the middle, gradually mix in 75ml of cold water, then pat and bring it together into a slightly tacky dough. Wrap and chill in the fridge for 1 hour.Peel the onion, quarter and core the apples, then finely slice both. Remove the shelf from the air-fryer drawer, add the onion and apple, cook for 10 minutes at 200ºC to dehydrate, then tip out to cool. Replace the shelf.Spoon the piccalilli into a blender and blitz until fairly smooth. Put 2 tablespoons into a bowl with the mince and a pinch of salt and black pepper, pop some into a cute dipping bowl for later, then pour the rest back into the jar and keep in the fridge for up to 3 weeks, for future meals.Once cool, chop the apple and onion, then add to the bowl of mince and scrunch it all together really well. Divide and flatten into 4 equal-sized rounds. Cut the dough into 4 equal-sized pieces, then, one by one, roll out between two sheets of greaseproof paper until just under ½cm thick and about 15cm wide. Sit one of the rounds of filling in the centre of each piece of pastry, then bring it up at the edges to hug the filling, folding and tucking it around in waves and crimps, and leaving some of the filling exposed.Beat the egg, eggwash the exposed pastry, and sprinkle the sesame seeds on to the pastry only. Grate the cheese and sprinkle over the exposed filling, then lift the pies into the air-fryer drawer and cook for 15 minutes at 200ºC, or until the pastry is golden and the filling is cooked through.Serve with the blitzed piccalilli. Great with a carrot, apple and walnut salad.This recipe is for a 1-drawer air fryer.