Preheat oven to 325 degrees F°.
Whisk egg* in large bowl then pour in maple syrup, melted coconut oil, nut butter, vanilla and almond milk, and whisk once more. *If using flax egg, mix 1 tbsp ground flaxseeds with 3 tbsp water & let sit for 5 minutes before adding to recipe in place of egg.
Stir in almond flour, collagen if using, baking soda, cinnamon & some of the sea salt.
Fold in chocolate chips (leave some aside for the topping), graham crackers and half of the marshmallows to save some for the topping.
Very lightly spray a 8 or 9-inch cast iron skillet (13-inch if doubling the recipe) with coconut oil then pour batter into the base & spread out evenly using a silicone spatula.
Place last pieces of chocolate and marshmallow over the top, sprinkle sea salt, then bake in oven for 19-20 min on center rack.
Then, turn oven on broil & cook 1- 1 1/2 additional minutes **keep a close eye on it because it can burn quickly! Enjoy!