Preheat your oven to 325°F (165°C) and prepare two 9-inch round cake pans by greasing them with butter or a non-stick spray and lining the bottoms with parchment paper.

In a mixing bowl, combine graham cracker crumbs, melted butter, and sugar until the mixture resembles wet sand. Press mixture firmly into the bottom of each cake pan and bake for 10-12 minutes until set. Remove from the oven and let cool.

In a large bowl, whisk together all-purpose flour, granulated sugar, Dutch-process cocoa powder, baking soda, baking powder, and salt until smooth.

In another bowl, mix together room temperature eggs, buttermilk, neutral oil, vanilla extract, and hot brewed coffee until smooth.

Gradually pour the wet ingredients into the dry ingredients, mixing gently until just combined. Divide batter evenly between the prepared pans.

Bake at 350°F (175°C) for 30-35 minutes, until a toothpick inserted comes out clean. Let cool in pans for 10 minutes before transferring to a wire rack.

To prepare the ganache, heat heavy cream until simmering. Pour over chopped dark chocolate and stir until smooth. Let cool slightly.

For the marshmallow frosting, combine egg whites and sugar in a heatproof bowl over simmering water. Whisk until it reaches 160°F (70°C) and sugar dissolves. Beat until glossy peaks form. Gradually add softened butter and marshmallow fluff.

Assemble the cake by placing one layer on a serving plate. Spread ganache on top, add second layer, and coat with marshmallow frosting.

Toast the marshmallow frosting with a kitchen torch until golden brown.

For the garnish, sprinkle extra graham cracker crumbs and mini marshmallows on top. Slice and serve.