Prepare the Apple Filling: In a medium saucepan, melt the unsalted butter over a medium heat until it shimmers. Add the finely diced apples and cook for 5-7 minutes, stirring occasionally, until the apples begin to soften and release their fragrant juices, turning slightly translucent.

Season the Filling: Stir in the demerara sugar, ground cinnamon, ground nutmeg, and a pinch of salt. Cook for another 2-3 minutes until the sugar has dissolved and the apples are beautifully coated and aromatic. In a small bowl, whisk together the cornflour and lemon juice to form a slurry. Pour this into the apple mixture and stir constantly for 1 minute until the filling thickens to a glossy, syrupy consistency. Remove from the heat and let it cool completely – this is crucial for preventing soggy pastry.

Prepare the Pastry: Unroll one sheet of chilled puff pastry onto a lightly floured surface. Using a 10cm (4-inch) round cutter or a sharp knife, cut out four circles or squares. Repeat with the second sheet of pastry to yield a total of eight pieces. You may need to gently re-roll scraps to get all 8, ensuring not to overwork the pastry.

Assemble the Hand Pies: Place a generous tablespoon of the cooled apple filling onto one half of each pastry circle or square, leaving a small border around the edge. In a small bowl, whisk the beaten egg with the milk (if using) to create an egg wash. Lightly brush the edges of the pastry with the egg wash. Fold the other half of the pastry over the filling to create a semi-circle or triangle, pressing down gently to seal the edges. Use a fork to crimp the edges firmly, ensuring no filling can escape. Make two small slits on the top of each hand pie with a sharp knife to allow steam to escape during cooking.

Air Fryer Preparation: Preheat your air fryer to 180°C (350°F) for 3-5 minutes. While preheating, brush the tops of the assembled hand pies generously with the remaining egg wash and sprinkle a little extra demerara sugar over each for a lovely caramelised crunch.

Air Fry the Hand Pies: Carefully place 2-4 hand pies in the air fryer basket, ensuring they are in a single layer and not touching to allow for proper air circulation. Cook for 12-15 minutes, flipping them halfway through, until the pastry is puffed up, deeply golden brown, and delightfully crisp to the touch, and the kitchen is filled with the sweet, spiced scent of baked apples. You'll hear a gentle sizzle as the sugar on top caramelises. Repeat with the remaining hand pies. Allow them to cool on a wire rack for a few minutes before serving. A dusting of icing sugar is a lovely optional touch.