Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy.
Beat in the egg and vanilla extract until fully incorporated.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the chocolate chips and graham cracker crumbs, ensuring they are evenly distributed throughout the dough.
With a cookie scoop or tablespoon, portion out half of the cookie dough onto the prepared baking sheet, leaving enough space between each cookie for spreading.
Press a few mini marshmallows into the center of each cookie portion and top them with another scoop of cookie dough, sealing the marshmallows inside.
Gently flatten the cookies slightly and sprinkle a few additional chocolate chips and graham cracker crumbs on top for decoration.
Bake in the preheated oven for 10-12 minutes, until the edges are golden brown. The centers may look a little soft; they will continue to cook on the baking sheet.
Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Notes
Serve the cookies warm and gooey, stacked on a platter with a drizzle of melted chocolate over the top. Add a few graham crackers as a decorative touch!