Prepare the cake. Prepare your baking dish for nonstick. Spray should work in this recipe. Then baked the cake according to the directions on the packaging and allow the cake to fully cool.
Poke. To poke the holes in the fully cooled cake, use the round handle of a wooden mixing spoon. Poke the holes in the cake, making the holes about a half inch apart and two thirds of the way into the cake (not all the way through the cake).
Pudding. In a medium sized mixing bowl, use a whisk to combine together the pudding mix and milk until smooth and lump-free. Carefully pour the mixture over the poked holes in the cake, making sure that it gets into all of the poked holes. You can use the backside of a spoon to move the pudding around so that the top of the cake and the holes get well covered. Refrigerate the cake for two hours so that the pudding can set over the cake and in the holes.
Frosting. In a large mixing bowl, beat the butter until until fluffy and smooth (about two and a half to three minutes). Then mix in the marshmallow fluff (a rubber spatula is helpful), vanilla extract, and salt until combined followed by the powdered sugar.
Topping. Use a large spoon or scoop to drop dollops of the frosting over the cake. Then you can use a frosting spatula or similar item to evenly spread the frosting over the entire top of the cake.
Serve Decorate the cake with the marshmallows, graham cracker crumbs, and chocolate. The cut the cake into pieces and serve.