Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the softened butter, granulated sugar, and brown sugar. Beat on medium speed until creamy and light in color, about 2-3 minutes.
Add the egg and vanilla extract to the butter mixture. Mix until well combined.
In a separate bowl, whisk together the all-purpose flour, graham cracker crumbs, salt, and baking soda. Gradually add to the wet mixture, mixing until just combined.
Gently fold in the semi-sweet chocolate chips, chopped Hershey bars, and mini marshmallows until evenly distributed.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, leaving space between each cookie.
Bake in the preheated oven for 10-12 minutes, until the edges are lightly golden. The centers may look slightly underbaked.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
