A giant S'mores cookie made in a cast iron skillet.
In an 8 or 9-inch cast iron skillet, melt the butter over medium-low heat. Whisk in the white sugar and brown sugar until smooth.
Remove from heat and allow the skillet to cool for 5 minutes (just until it's not hot; warm is okay).
Add in the vanilla and egg. Mix until combined. Add in the flour, baking soda, salt, and chocolate chips. Mix until combined.
Smooth around the skillet making the center higher than the edges (edges tend to rise more).
Bake for 20 minutes. Remove and crumble the graham cracker sheets on top and press the miniature marshmallows into the cookie. Bake for another 5-10 minutes or until cooked through and golden around the edges (it should still be soft and slightly under-baked in the center).
Remove and enjoy immediately!