Cut the unsalted and salted butters into 1/2 inch cubes and combine with the brown and granualted in the bowl of your stand mixer with the paddle attachment. Mix in the egg and vanilla extract.
In a separate large bowl, whisk together the flour and baking soda. While mixing on low, add the flour+baking soda into your stand mixer. Next add in your pretzel pieces, marshmallows, and chocolate chips + chocolate pieces and mix just until combined. (Remember to reserve some pretzels, marshmallows, and chocolate pieces for placing on top of the cookie dough before baking).
Use a 2 inch cookie scoop to scoop out cookie dough balls and place on a parchment lined baking sheet. Add a few marshmallows, pretzel bits and chocolate pieces to the top of each cookie and push in, while keeping the cookie rounded. Refrigerate overnight.
When ready to bake, place 4 cookie dough balls per parchment lined baking sheet. Preheat oven to 350°F. Bake for about 8-10 minutes total, while pan banging (lift up the pan with your oven mitts on, inside the oven at 4, 6, and 8 minutes, and drop it) to get the cookies extra thin and crispy with the crinkles around the edges. Remove and let cool one minute on pan before removing to a cooling rack to cool completely for 20 minutes.