Preheat the oven to 350F then line a 9x13 inch baking pan with aluminum foil. Spray with nonstick cooking spray and set aside.
Add the graham cracker crumbs to a large bowl, mix in the sugar, and the salt to combine. Pour the melted butter on top and mix again until everything is well coated.
2 cup graham cracker crumbs, 1/4 cup granulated sugar, 1/4 tsp salt, 1/2 cup butter
Pour the graham cracker mixture into the prepared pan and using a rubber spatula or the back of a measuring cup gently spread the crumbs out to an even layer. Bake in the oven for 10 minutes. Remove from the oven and turn it off.
Place the chocolate bars on top of the warm graham cracker crust and place back in the warm oven for a few minutes or until the chocolate is melted.
4 (4.4oz) packages Hersheys chocoolate bars
Add the marshmallows on top of the chocolate and place in the oven, turn on the broiler and broil just until the marshmallows are brown.
10 oz mini marshmallows.
Allow the bars to set in the fridge for a few minutes before slicing into them.