Place chocolate squares in middle of puff pastry and top with marshmallows and slice pastry evenly on an angle.
Fold pastry strip by strip so it looks like plated, see picture. Then place another sheet of pastry underneath, this will help soak and catch any oozing choc and marshmallow.
Spray lightly with cooking spray and then sprinkle some cinnamon sugar over top.
Place into a lined slow cooker that has been pre-warmed for about 1/2 hour on high. The with a tea towel under the lid, cook on high for 2 hours or until pastry is cooked.
Brown under the grill to get a more brown colour and crisp the top up a little more.