Preheat your oven to 350 degrees.
Cream together your butter, brown sugar and sugar until smooth.
Add in your peanut butter and mix till smooth.
Add in your eggs and vanilla and stir well.
In a separate bowl, crush your graham crackers into small pieces.
Add your flour, baking powder, and salt into the bowl with your graham crackers.
Dump your dry ingredients in with your wet ingredients and stir till just combined.
Fold your peanut butter cup pieces and your chocolate chips into your batter.
Scoop your batter from the bowl into a sprayed 9x13 baking pan and spread with a rubber spatula to even it out.
Bake your cookie bars for about 30 minutes, until edges turn golden and an inserted toothpick comes out clean.
Sprinkle marshmallows over the top of your cookie bars.
Place back into your oven and turn to broil. Cook for about 1 minute, but watch super closely till the marshmallows are just toasted.
Sprinkle with a couple extra pieces of peanut butter cups and chocolate chips for decoration (optional).
Allow to cool, and slice into pieces and serve. (Spray your knife with pam in between each slice to keep marshmallows off as much as possible).