Make caramel. Cool completely.
Preheat oven to 200 C / 400 F. Line a large baking tray with baking paper.
Cut puff pastry sheets into 4 equal squares.
Place one pastry sheet square on a flat work surface.
With one pointy edge of the sheet pointing towards you, fold it in half.
Make two slits on both sides. Open to make it a square.
Cross the slits to the opposite sides to create a diamond shape.
Continue with the remaining pastry sheets.
Transfer to the baking tray.
Brush caramel inside the diamond shapes.
Arrange apple slices on top.
Top with more caramel.
Brush the sides of the pastries with whisked egg.
Bake for about 20-25 minutes or until golden.
Before serving, top with more caramel if you like.