Preheat your oven to 350°F (175°C). Grease two 9-inch round cake pans, line the bottoms with parchment circles, and lightly grease the parchment.

In a large bowl, whisk together 2 cups flour, 2 cups sugar, 3/4 cup cocoa powder, 2 teaspoons baking soda, and 1 teaspoon salt until evenly combined.

In a separate bowl combine 2 large eggs, 1 cup milk, 1 cup vegetable oil, and 1 1/2 teaspoons vanilla. Whisk until smooth.

Pour the wet mixture into the dry ingredients and beat on low until just combined.

Slowly add 1 cup hot water while mixing at low speed. The batter will be thin — that's normal and yields a moist, tender crumb.

Divide the batter evenly between the prepared pans. Smooth the tops gently with an offset spatula.

Bake for 28 to 35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.

Let the cakes cool in the pans for 10-15 minutes, then invert onto cooling racks and remove the parchment. Cool completely before assembling.

Combine 3/4 cup graham cracker crumbs and 1 1/2 tablespoons sugar in a bowl, then stir in 1/4 cup melted butter until the crumbs are evenly moistened.

Spread the mixture thinly on a baking sheet lined with parchment and bake at 350°F for 8-10 minutes, or until lightly golden and fragrant.

Let cool completely; then pulse in a food processor for a slightly finer texture if you prefer.

In the bowl of a stand mixer fitted with the paddle or whisk attachment, beat 1 3/4 cups room-temperature unsalted butter on medium speed until pale and fluffy.

Add 3 1/4 cups marshmallow fluff in two additions, beating briefly after each to combine.

Gradually add 6 cups sifted powdered sugar, about a cup at a time, beating on low until incorporated.

Raise speed to medium-high and beat until the frosting is light and smooth.

Add 1 teaspoon vanilla and a pinch of salt to balance the sweetness.

If the buttercream seems too stiff, add a little milk, 1 teaspoon at a time, until spreadable.

Optional: fold in 1 1/2 cups mini marshmallows for pops of chew and extra texture.

Place 9 oz semi-sweet chocolate chips in a heatproof bowl.

In a small saucepan, heat 3/4 cup heavy whipping cream until it just begins to simmer around the edges — do not boil.

Pour the hot cream over the chocolate chips and let sit for 1-2 minutes to soften, then gently stir until smooth and glossy.

Allow the ganache to cool and thicken slightly at room temperature until it’s pourable but not runny.

Beat 3/4 cup room-temperature unsalted butter until creamy.

Gradually add 3 cups powdered sugar and beat on low to combine.

Mix in 1 teaspoon vanilla and 1 tablespoon milk to reach a spreadable consistency.

Level the cake layers if needed so they stack evenly. Place one layer on your cake board or serving plate.

Spread a generous layer of the toasted marshmallow buttercream on the first cake layer.

Sprinkle a layer of graham cracker crunchies over the buttercream.

Add the second cake layer on top and press gently to level.

Apply a thin crumb coat using the vanilla smoothing frosting or a light layer of marshmallow buttercream.

Chill the cake in the refrigerator for 20-30 minutes to set the crumb coat.

Once chilled, spread a thicker, final layer of marshmallow buttercream around the top and sides.

Pour the slightly cooled ganache over the top center of the cake and gently nudge it toward the edges.

Sprinkle additional graham cracker crunchies along the top and sides where the ganache meets the frosting.

For a campfire effect, use a kitchen torch to carefully toast the marshmallow garnish until golden brown.

Chill the assembled cake for at least 30 minutes so the frosting firms and the ganache sets.

For clean slices, remove the cake from the refrigerator 20-30 minutes before serving.