Preheat oven to 350 degrees. Grease a 9-inch pie pan with cooking spray or butter. Set aside.
Add butter and sugar to the bowl of a stand mixer, fitted with a paddle attachment. Cream together on medium until smooth and fluffy (about 2 minutes). Add the vanilla and egg and continue on low until combined. Set aside while we mix the dry ingredients.
Grab graham crackers and place them in a medium mixing bowl. Crush them with a potato masher until you have chunks of cracker the size of grapes. Any smaller that that and you won't taste the graham cracker as much. Add flour, baking powder, and salt. Mix until combined.
Add 1/3 of the dry ingredients to the wet ingredients. Mix on medium-low until combined. Repeat with the next 1/3 and then the last 1/3.
Cut dough into even thirds. Take 2/3 of the dough and press it into the prepared pie pan so that it is covering the entire bottom, evenly. Spread marshmallow cream all over the dough. This will be tricky since the creme is so darn sticky! To make it easier, spray a spatula with nonstick spray.
Sprinkle marshmallow creme with chocolate chips and mini marshmallows, Grab remaining 1/3 of dough and form into a large disk, using both hands to flatten and shape it. There won't be enough dough to completely cover the marshmallow and chips but that's okay. It actually looks better with some of the filling exposed. Sprinkle a few more chocolate chips on top.
Bake the cookie cake for 25 minutes until the crust is golden brown and the marshmallow has started caramelizing.
Let cake sit for 20-30 minutes until it's cooled somewhat. It is hard to slice when it first comes out of the oven so letting it sit will let the filling harden a bit.