Preheat the over to 350 degrees and make sure your 12-inch skillet is well seasoned. (You can also rub some oil with a paper towel so that the bottom and sides of the skillet are shiny but not drenched in oil.)
In the bowl of an electric mixer (or using a hand held mixer), cream together butter and sugar or a couple of minutes.
Add egg and vanilla and beat until mixed.
Sift in the flour, baking soda, and salt. Mix the ingredients on low speed until just combined.
Spread cookie batter on the skillet, evenly.
Spread marshmallows and chocolate chips evenly over the top.
Crush graham crackers and spread that over the marshmallows and chocolate chips.