- 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. 
- Spread the mixture evenly in the prepared baking dish. 
- 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 squares.