Preheat oven to 350 degrees and grease an 8x8 or 9x9 pan.
Place graham crackers into a zip bag,seal the bag,and roll over it with the rolling pin until crumbs are formed. The crumbs don't need to be ultra fine - a few chunks work okay.
In a medium bowl, mix the crumbs with the butter and sugar.
Set aside ¼ of the crumb mixture to use as the topping.
Press the rest of the crumb mixture into the prepared pan and bake for 10 minutes.
Remove from oven and carefully top with pieces of chocolate bars.
Place back in oven for 5 minutes.
Remove and spread chocolate with a spatula to cover the crust.
Top with 12 square marshmallows and bake for 6 minutes.If you do not have square marshmallows, just cover the chocolate layer with whatever marshmallows you have on hand.
Bake for 6 minutes.
Remove from oven, top with remaining crumb mixture and bake for a final 6 minutes.
When bars are done, cool in refrigerator for 30 minutes or until they can be easily cut into bars.