Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking dish.
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, mini marshmallows, and graham cracker crumbs until evenly distributed.
Spread half of the cookie dough mixture evenly into the prepared baking dish.
Sprinkle the remaining chocolate chips on top of the first layer, then drop spoonfuls of the remaining cookie dough over the chocolate chips.
Bake for 25-30 minutes, or until the edges are golden brown and the center is set.
Allow to cool in the pan for at least 15 minutes before cutting into bars.