Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a large bowl, whisk together the flour, graham cracker crumbs, baking powder, baking soda, salt, cocoa powder, sugar, and brown sugar until well combined.
In a separate bowl, beat the eggs, then add the milk, vegetable oil, and vanilla extract. Mix until smooth.
Gradually add the wet mixture to the dry ingredients, stirring until just combined. Fold in mini chocolate chips for an extra treat in each cupcake.
Divide the batter evenly among the cupcake liners, filling each about 2/3 full.
Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean.
Let the cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
In a large bowl, beat the softened butter until creamy. Gradually add the powdered sugar and mix until combined. Add the mini marshmallows, milk, and vanilla extract, and beat until the frosting is light and fluffy.
Once the cupcakes are completely cool, generously frost each with the marshmallow frosting.
Place half a marshmallow on top of each frosted cupcake. If desired, use a kitchen torch to lightly toast the marshmallow for that campfire flavor.
Notes
For an extra touch, lightly toast the marshmallows on top.