Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chocolate chips and graham cracker crumbs. Reserve a small handful of chocolate chips and graham cracker crumbs for topping.
Spread half of the cookie dough evenly in the prepared baking pan. Sprinkle the mini marshmallows over the dough, followed by the reserved chocolate chips and graham cracker crumbs.
Top with the remaining cookie dough, spreading it gently to cover the marshmallows and toppings.
Bake for 25-30 minutes, or until the edges are golden brown and a toothpick inserted in the center comes out clean.
Allow to cool in the pan for at least 15 minutes before cutting into bars.