Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking dish.

In a large mixing bowl, cream the softened butter, brown sugar, and granulated sugar until fluffy.

Add eggs one at a time and then mix in the vanilla extract until smooth.

Whisk together the flour, baking soda, and salt in a separate bowl, then gradually incorporate it into the wet ingredients.

Fold in the chocolate chips and graham cracker crumbs with a spatula.

Spread half of the cookie dough mixture into the prepared baking dish for the base layer.

Sprinkle mini marshmallows evenly over the cookie dough base.

Drop spoonfuls of the remaining cookie dough over the marshmallows, ensuring some marshmallow is visible.

Bake for 25-30 minutes or until golden brown and a toothpick comes out clean.

Allow to cool completely on a wire rack before slicing into squares.