I wasn't sure how many graham crackers it would take to make 2 cups of crumbs, so Grace and I crumbled a whole sleeve of graham crackers. It came out to almost 4 cups. We stirred all of them into the package of cookie mix.
Mix the cracker mixture with the melted butter and stir until a soft dough forms.
Press into a 9×13 pan.
Bake for 20 minutes or until set.
As soon as the cookie comes out of the oven, sprinkle the chocolate chips over the whole thing.
Wait a few minutes, then use a butter knife or spreader to make the chocolate chips into a single melted chocolate layer.
Preheat oven to broil.
Sprinkle the marshmallows over the chocolate. (Don't use extra marshmallows like I did; it makes the finished bars much harder to eat.)
Broil the cookies about 5 inches from the heat. Broil for 30 seconds at a time, checking frequently as the mini marshmallows will toast and catch on fire quickly. Not that I caught mine on fire, mind you. I'm just throwing that out there.
Cool for 10 minutes, cut into 20 bars, and serve hot.