Preheat oven to 350 degrees.

Lightly grease three 8 inch cake pans.

In a large mixing bowl combine the 2 cake mixes, graham cracker crumbs, water, oil and eggs.

Whisk until smooth and all combined.

Divide the batter evenly between the 3 pans.

Bake at 350 for 20-25 minutes or until a toothpick inserted comes out clean.

Let the cakes cool in the pans for 5 minutes before transferring from the pans to a cooling rack.

Cool the cakes completely.

Meanwhile prepare the buttercream.

Turn your oven to broil.

Line a baking sheet with foil and spray with non-stick spray.

Spread out the 4 cups of mini marshmallows on the baking sheet.

Place the marshmallows under the broiler.

Do not take your eyes off the marshmallows while they are under the broiler. It will only take them a minute to get toasted.

Remove the marshmallows from the oven and immediately add to a large mixing bowl.

To the bowl add your softened butter and using an electric mixer whip the butter and marshmallow together.

Next carefully add the powdered sugar a little at a time.

Once all the sugar is added, whip the frosting for 5-7 minutes until light and fluffy.

Next prepare to frost your cake.

Place a cake layer onto your serving plate or cake plate.

Frost the top of that layer with a layer of the marshmallow buttercream.

Top that with half of the hot fudge sauce. The buttercream and the fudge sauce will mix a little and that's okay.

Repeat with the next layer.

Place the final layer on top and frost the whole cake with the marshmallow buttercream. If you like you can reserve some frosting and pipe a bit on the top for decoration.

In a small microwave safe bowl warm your heavy whipping cream in 30 second increments until hot.

Add your chocolate chips to the cream and let sit for 5 minutes before whisking together. Whisk until smooth and glossy.

Let the ganache cool slightly and drizzle it around the top edge. You can also use a piping bag or ziploc bag with the tip snipped for this.

I like to take some graham cracker crumbs and sprinkle them around the bottom half of the cake. I then decorate the top with graham crackers, hershey bars and more marshmallows though this is optional.

Serve!