Preheat your oven to 375 degrees F. Spray three 8-inch or four 6-inch round cake pans with non-stick spray and then line with parchment. Spray again. Set aside.

In a medium sized bowl combine the graham cracker crumbs, melted butter and sugar. Stir until all the graham cracker crumbs are damped by the melted butter.

Divide evenly between the three pans and press down firmly with your hand or the back of a spoon.

Combine the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined.

In another bowl, combine the buttermilk, oil, eggs, water and vanilla.

With the mixer on low speed, slowly add the wet ingredients to the dry, scraping the bottom of the bowl with a rubber spatula.

Cool in the pans for 10 minutes, then turn them out onto a cooling rack and cool completely.

Wrap in plastic wrap and chill until ready to use. 

Place the marshmallows on a cookie sheet lined with parchment paper and sprayed with nonstick cooking spray. Place on the middle rack of the oven, and broil the marshmallows until golden brown on top, about 30-60 seconds. Keep your eye on them!

Remove the pan from the oven and gently turn the marshmallows over and broil them again until they are golden brown on the other side.

In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and powdered sugar and beat on low until blended. Add the vanilla and mix on medium speed for about three minutes

With the mixer on low speed, add the marshmallow cream and (cooled) toasted marshmallows, and mix for about one minute. 

In a microwave safe bowl, pour the cream over the chocolate chips and heat for about 45-60 seconds. Stir, and if needed, heat for another 30 seconds to melt the chocolate chips completely. Let cool to room temperature before using.

In the bowl of a standing mixer, whisk the eggs and salt until fluffy and frothy.

Meanwhile, heat the sugar, corn syrup, water and vanilla paste. Heat over medium flame until the sugar is dissolved and just simmering, about 5 minutes.

With the mixer on medium speed, add a tiny bit of the hot sugar mixture to the egg whites at a time. (Temper the eggs - don't scramble the them)

Eventually, all of the sugar will be added and then turn the mixer up to high. Beat the mixture on high for about 5 minutes or until very stiff and shiny. 

Best used right away. 

When you're ready to frost the cake, bring the frosting back to room temperature and mix by hand with a wooden spoon to push out all of the air pockets. 

Level each chocolate cake layer, if needed, and then place the first cake layer, graham cracker side down, on a cake board.

Spread half of the chocolate ganache on the cake layer and then freeze for 5 to 10 minutes to set the ganache a little.

Carefully spread half of the toasted marshmallow filling over the chocolate ganache and repeat step 2 and 3 for the second cake layer.

Place the final cake layer, graham cracker side down, on top and cover with a crumb coat layer of the chocolate frosting. Freeze the cake for 10 to 15 minutes to set the crumb coat.

Finish frosting the cake with the chocolate frosting and then decorate the top of the cake with the marshmallow fluff, toasting with a kitchen torch, if desired.