Prepare the brownie mix as instructed on the package and then set aside.
Spray a 9x9 dish with nonstick cooking spray or cover with parchment paper.
Crumble up about 8 graham crackers.
Coat the bottom of the pan with about half of the crumbled graham crackers.
Pour the brownie mix evenly on top of the crumbled cookies.
Bake for 30-40 minutes or until when a toothpick is inserted it comes out clean. The baking time will depend on the brownie mix that you are using, be sure to read the box for the baking times.
Remove from the oven and top with the marshmallows, remaining cookie crumbs, and pieces of chocolate bar.
Put back in oven for another 5-10 minutes until marshmallows are slightly browned.
Serve.
Notes
This recipe uses the brownie mix plus the ingredients on the box to make the mix. The nutritional values will vary depending on the mix you use.