Preheat the oven to 350 degrees Fahrenheit and prepare an 8 inch cast iron skillet by spraying it with cooking spray.
Take the salted butter, light brown sugar and granulated white sugar, and beat them together in a bowl until fully combined and light and fluffy, about 1-2 minutes.
Whisk in the eggs, and vanilla extract. Stir until fully combined.In a separate bowl, whisk together the all-purpose flour, baking powder, salt, and baking soda.
Pour the bowl of dry ingredients into the wet ingredients bowl and mix until just combined.
Fold in the semi-sweet chocolate chips, dark chocolate chips, and half of the graham crackers.
Take half the cookie batter and press it into the bottom of the cast iron skillet. Be sure to cover the entire bottom of the skillet.
Spread ½ cup of the divided mini marshmallows over the cookie dough.
Place remaining cookie dough batter atop the marshmallows. Cookie dough will spread, so it is okay if it doesn’t cover everything completely; just try to spread it out evenly.
Top the cookie dough with the chocolate bar squares and the remaining graham crackers.
Bake in the oven for 15 minutes. Take out and top the cookie dough with the remaining ½ cup mini marshmallows. Put back in the oven.
Bake for an additional 10-15 minutes or until the cookie is golden brown with a little jiggle.
Let sit for 15-20 minutes before plating and serving. The cookie will continue cooking once it’s out of the oven, so it’s important to wait and let it continue cooking once it’s out of the oven or you will have raw cookie dough in the center.