Preheat oven to 200ºC (390ºF). Place the apple, sugar, cinnamon and butter in a small bowl and mix to combine. Cut the pastry into 4 equal squares and score the edges to create a 1cm border. Layer with the apple mixture and brush with the egg. Place on a baking tray lined with non-stick baking paper and cook for 10–15 minutes or until golden and puffed. Serve with double cream or ice-cream. Serves 4.