Adjust oven rack to middle position. Preheat oven to 350 F and line two baking sheets with parchment paper.

In a small bowl, combine flour, baking powder, baking soda, salt, and cinnamon. 

In the bowl of a stand mixer with the paddle attachment, beat together the butter, sugar, and 1/2 cup of the graham cracker crumbs. Beat on medium-high speed for 2-3 minutes or until mixture is light and fluffy. Scrape down the sides then add egg and vanilla. Mix until just combined. Add dry ingredients and let mix on low speed until dry mixture is combined and no dry flour remains. 

Place remaining graham cracker crumbs in a shallow dish. Scoop out dough, one tablespoon at a time, and roll into a ball. Roll the dough balls in the graham cracker crumbs to coat them well. Place them on a baking sheet, evenly spaced (12 cookies per sheet). If you end up with 25 cookies, just arrange the cookie in the middle of the cookie rows, making sure it's not close to the other cookies. 

Bake one sheet of cookies at a time for 10-12 minutes. The cookies will be set and just barely starting to crack. Remove the cookies from the oven. Place the other batch in the oven and allow the first batch of baked cookies to cool on the rack for 5 minutes. Top baked cookies with halved marshmallows, cut side down on the cookie. 

After the second batch has baked, remove, allow to cool, then top with marshmallows. Move baking rack so it is sitting about 10" from the broiler and preheat the broiler. Place the cookies under the broiler for 30-45 seconds, rotating halfway through. The marshmallows should be a deep golden brown. Remove from oven, move to a cooling rack, and top with mini peanut butter cups, widest side down. Repeat process with second tray of cookies. You can eat the cookies warm from the oven or allow them to completely cool. Enjoy!