Preheat the oven to 220 degrees Celsius.
Peel the apples, remove the core and cut into thin strips. Transfer them into a large bowl.
Add the ground cinnamon and black raisins into the apple strips, and toss well.
Put the sugar in a saucepan. Melt the sugar over medium heat until the sugar caramelises and turns amber in colour. Turn down the heat and add in the butter and salt. Stir the sugar mixture well.
Add the apple strips, raisins and ground cinnamon to the sugar mixture. Cook over medium heat for about 10 minutes, until the apples are softened (but not mushy).
Mix the corn flour and water well. Add it to the apple mixture when it is bubbling over the heat. The apple mixture should be thickened. Transfer to a bowl and set aside to cool.
Place a sheet of the thawed puff pastry on your work surface. Place the filling along half of the puff pastry, leaving an approximate 2.5cm space along the 3 edges.
Chef’s tip: Do not remove the puff pastry from the refrigerator too early. This will cause the pastry to be too soft and the sheets may stick together.
Brush the 3 edges with some egg wash and fold over half of the puff pastry. Using a fork, press down the edges to seal up the sides and make a pattern.
Brush the puff pastry with the egg wash.
Combine the caster sugar and ground cinnamon, and sprinkle it on top of the pastry.
Carefully lift the pastry and place it on the tray in the oven and lower the temperature to 200 ̊C.
Bake the pastry for 10-12 minutes, until golden. Serve immediately with ice cream.