Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt. Set aside.
In a large mixing bowl, cream together softened butter, granulated sugar, and brown sugar until light and fluffy.
Add in the egg and vanilla extract to the butter-sugar mixture, mixing until well combined.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
Fold in the mini chocolate chips for an extra chocolatey kick.
Take about a tablespoon of dough and flatten it in the palm of your hand. Place a few mini marshmallows and a sprinkle of graham cracker crumbs in the center, then top it with another tablespoon of dough. Seal the edges by rolling it into a ball.
Place the cookie dough ball on the prepared baking sheet and repeat with the remaining dough, leaving enough space between each cookie to spread.
Bake for 10-12 minutes, or until the edges are firm but the centers are still soft. Remove from the oven and let them cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Notes
Serve the cookies warm on a rustic wooden board, with a side of additional graham cracker squares and chocolate bars for a complete s’mores experience!