In the pan, combine sugars and oil. Add eggs and vanilla, and mix. Add flour, baking soda, and salt and mix to combine. Add the chocolate chips and combine.
Press ⅔ of the cookie dough into the pan (about 2.5 cups of dough).
Grease a spatula and use it to spread the marshmallow fluff across the cookie dough. (Try to place a few dollops over the pan so it’s easier to spread than if it’s all in the center.)
Crumble graham crackers and sprinkle on top of fluff.
Crumble cookie dough and place on top of graham cracker crumbs.
Bake for 40-45 minutes. (We tested this in disposable pans. Baking time will be less in a glass or metal pan.) Chill completely before slicing.