Preheat your oven to 350ºF.
Line your baking sheet with parchment paper or a silicone baking mat.
Cut your Hershey's bar in big chunks. If using larger marshmallows, cut them into quarters. If you're using mini marshmallows, leave it as is. Crush your graham crackers as well. (See tips and tricks below on how to crush graham crackers.) Set aside.
In a large bowl, add the crushed graham crackers, flour, baking soda, baking powder, and salt and mix until well combined. Set aside.
Using your stand mixer fitted with the paddle attachment, cream together the softened butter, white sugar, and brown sugar. Mix until creamy, smooth, and combined. This should take about 3 minutes or so.
Add in your eggs, one at a time, and then add the vanilla extract. Mix until combined.
Slowly add the dry ingredients to your mixer and mix until combined.
Fold in your chocolate chips.
Scoop your dough onto your baking sheet, making about 1 inch balls.
Bake for 8 minutes.
Take the cookies out of the oven and very carefully add the chopped Hershey's bar and marshmallows to each cookie. Add as many or as little you would like.
Bake for another 4 minutes.
Let the cookies cool on the baking sheet for 10 minutes before touching them.