Preheat your oven to 400 degrees Fahrenheit.
Grease a standard muffin tin thoroughly with non-stick spray.
Cut the thawed puff pastry sheets into twelve equal squares.
Press one pastry square into each muffin well.
Peel and dice the apples into uniform half-inch cubes.
Toss the diced apples with brown sugar and cinnamon in a bowl until coated.
Spoon the apple mixture evenly into the pastry-lined muffin cavities.
Brush the exposed edges of the pastry with a beaten egg.
Bake for 20 minutes until the pastry is deep golden brown and apples are tender.
Remove from the oven, cool slightly, and drizzle with warm salted caramel sauce before serving.