Preheat your oven to 350°F (175°C) to ensure even baking.
Cream together the butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.
Add the egg, egg yolk, and vanilla extract to the mixture and beat until well combined.
In another bowl, whisk together the flour, graham cracker crumbs, baking soda, and salt. Gradually add this to the wet mixture, stirring until just combined.
Fold in the chocolate chips, chopped Hershey's chocolate, and mini marshmallows gently to keep marshmallows intact.
Using a spoon or cookie scoop, portion out the dough onto a baking sheet lined with parchment paper, leaving space between each cookie.
Bake for 10-12 minutes, or until the edges are golden brown. The centers will look slightly underbaked.
Let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.
