Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.
In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar with an electric mixer until light and fluffy, about 3-4 minutes.
Beat in the eggs one at a time, then mix in the vanilla extract until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed or folding gently with a spatula. Avoid overmixing.
Fold in the semisweet chocolate chips and crushed graham crackers evenly into the dough.
Drop rounded tablespoons of dough onto the prepared baking sheets, spacing about 2 inches apart.
Top each cookie dough ball with a generous amount of mini marshmallows.
Bake for 10-12 minutes, until edges are set and marshmallows are toasted golden brown. Watch closely to prevent burning.
Let cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely before enjoying.