Step 1: Preheat the Oven
• Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.

Step 2: Prepare the Cookie Dough
• In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
• Beat in the eggs one at a time, followed by the vanilla extract.
• In another bowl, whisk together the flour, baking soda, salt, and graham cracker crumbs.
• Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the chocolate chips and mini marshmallows.

Step 3: Bake the Cookies
• Use a cookie scoop or tablespoon to drop dough onto the prepared baking sheets, spacing them about 2 inches apart.
• Bake in the preheated oven for 12–15 minutes, or until the edges are lightly golden. The centers may look slightly underbaked; they will firm up as they cool.
• Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.

Step 4: Prepare the Frosting
• In a medium bowl, beat the softened butter until creamy.
• Gradually add the powdered sugar and cocoa powder, mixing until combined.
• Pour in the milk and vanilla extract, and beat until smooth and fluffy. Adjust the consistency with more milk or powdered sugar if needed.

Step 5: Frost the Cookies
• Once the cookies are completely cooled, spread a generous amount of frosting on top of each cookie.
• Sprinkle extra mini marshmallows on top of the frosted cookies.