Roll out the puff pastry dough into a large rectangle (according to the amount of dough you have - try for approximately 9-inch by 18-inch or so).
Spread the peanut butter down the middle 1/3 of the rectangle (it might help to microwave the peanut butter for 15 seconds to make it more spreadable).
Place the chocolate pieces over the peanut butter evenly.
Add the mini marshmallows on top and sprinkle over the graham cracker crumbs as well.
Use a pizza cutter or sharp knife to create slits in the sides of the puff pastry rectangle and pull the side pieces over top of the filling ingredients in a braid style (watch the video at the beginning of this blog post for a full tutorial).
Whisk the egg and water together well in a small bowl.
Tuck in any edges of pastry dough and brush lightly with the egg wash.
Sprinkle the mini chocolate chips overtop of the strudel and bake at 350 degrees Fahrenheit for 20-25 minutes or until golden brown.