Layers of graham cracker crust, chocolate cake, chocolate ganache, toasted marshmallow filling, chocolate frosting and marshmallow fluff.
Bake for 5 minutes. Let cool while you make the chocolate cake batter.
Preheat the oven to 325 degrees F.
Pour the batter into the prepared pans (about 12 ounces in each 6-inch pan or 15 ounces in each 8-inch pan), over the cooked graham cracker crusts and bake for 25 to 30 minutes, or until a toothpick inserted in the center of the cake comes out with a few moist crumsb on it.
Heat the cream until nearly boiling in a microwave safe bowl. Pour the hot cream over the chocolate chips and stir until the chips are melted and the mixture is smooth. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter for about 2 minutes on medium-high speed.
With the mixer on low speed, add the ganache. Scrape down the sides and bottom of the bowl and then mix on medium-high speed for about a minute, until the mixture is smooth.
Gradually add the powdered sugar, one cup at a time, followed by the vanilla and salt.
Buttercream can be store in an airtight container in the refrigerator for a week.