Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large bowl, cream together the softened butter, peanut butter, granulated sugar, and brown sugar until smooth and fluffy.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
In another 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 mini marshmallows, milk chocolate chips, and graham cracker crumbs until evenly distributed.
Drop tablespoon-sized balls of 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.
Remove from the oven and let cool on the baking sheets for 5 minutes before transferring to wire racks to cool completely.
Once cooled, sandwich two cookies together with additional peanut butter or a layer of chocolate if desired.