Prep: Preheat oven to 350 degrees F. Rub a 10-12 inch, deep cast iron skillet with softened butter to lightly coat. Set aside.

Mix Cookie Dough: In the bowl of a stand mixer (or large bowl with an electric hand mixer), beat together butter with granulated sugar and brown sugar until smooth. Add eggs and vanilla extract and beat until just barely combined. In a separate bowl, combine flour, baking soda, and salt. Add the flour mixture to the egg mixture and combine. Fold in the chocolate chunks and graham cracker chunks. 

Build Skillet: Pour out 1/2 of the cookie dough into prepared cast iron skillet. Top with the marshmallows and then the rest of the cookie dough (you won't be able to spread it nicely over the marshmallows, so just large scoops will be fine) - try and cover the marshmallows as much as you can with just little bits peeking out.

Bake: Place in oven, middle rack, and let bake 22-27 minutes or until the edges start to turn light golden brown. 

Serve: Remove from oven and let cool before serving. Enjoy!