Preheat oven to 350 degrees F. Grease & flour or spray with non-stick spray, a 9x13 inch pan.
Combine cake mix and bake as called out on.
After cake has baked, let it cool about 5 minutes and poke the cake all over with the end of a wooden spoon.
In the 5 minute window, while the cake is cooling, prepare the the instant chocolate pudding mix and before it starts thickening, slowly pour 1/2 of the 1st chocolate pudding layer over the top making sure pudding gets in all the holes of the cake. Tap the bottom of the pan on counter lightly to allow the pudding to seep into the cake.
Cover cake and refrigerate.
Take reserved other half of chocolate pudding and add in 2 cups of cool whip and whip together, set aside. (If you don't want to add in the whipped cream that's fine, by adding it in, it's like a chocolate mousse layer, if you add it in.)
In another medium-sized bowl, take 2 cups of marshmallow cream and beat with mixer to soften (you can microwave 20-30 seconds if you want), then add in 1 tub of cool whip and whip lightly until mixed, (You can use a mixer at low speed.) and set aside.
Using a microwaveable dish, pour in 1/2 cup of heavy cream and 1 tablespoon butter and boil in microwave. add chocolate chips and let sit for 5 minutes and then whisk until smooth and shiny and set aside.
Take cake out of fridge and add the 2nd chocolate pudding/cool whip layer by spreading it out evenly.
Next add the marshmallow/cool whip layer on top of the pudding layer.
Add the graham cracker bits to the top and pour/drizzle the chocolate ganache on top of the cake and graham crackers. Add some mini marshmallows and again drizzle more chocolate ganache. Add some extra graham cracker crumbs and place cake in refrigerator to set up for 4 hours or so.