Make the ganache: Heat the heavy cream, chocolate and salt in a heatproof bowl set over a saucepan of simmering water (do not let the bowl touch the water), stirring occasionally, until the chocolate melts and the ganache is smooth. Stir in the vanilla. Remove the bowl from the pan and set aside until the ganache is cool and thick but still pourable, about 1 hour.

Meanwhile, make the filling: Preheat the oven to 350 degrees F. Toss the graham cracker crumbs, melted butter and salt in a bowl until combined. Spread out on a baking sheet. Bake, stirring occasionally, until toasted, 8 to 10 minutes; let cool.

Assemble the cake as close to serving time as possible: Using a long serrated knife, carefully slice each cake layer in half horizontally. Place 1 cake half on a platter. Using a lightly oiled offset spatula or spoon, spread one-third of the marshmallow cream on top, stopping about 1 inch from the edge (if the marshmallow cream is difficult to spread, microwave 10 to 15 seconds to soften). Sprinkle one-third of the graham cracker mixture over the marshmallow cream. Repeat to make 4 layers, ending with cake; reserve a few tablespoons of the graham cracker mixture for topping.

Pour the ganache over the cake, letting it drip down the sides. Sprinkle with the reserved graham cracker mixture. Serve immediately.

Photograph by Levi Brown