Preheat the oven to 350°F.

Crush the graham crackers into fine crumbs using a food processor or a ziplock bag and rolling pin.

Mix the crumbs with melted butter and sugar until well combined.

Press about 2 tablespoons of the mixture into the bottom of each lined cupcake tin, forming an even layer.

Bake for 8 minutes, then set aside to cool.

In a bowl, whisk together sugar, flour, cocoa powder, baking soda, baking powder, and salt.

Add the egg, vanilla, buttermilk, and oil, stirring until well combined.

Slowly mix in the hot coffee until the batter is smooth. It will be thin.

Pour the batter over the cooled graham cracker crusts.

Bake at 350°F for 20 minutes, or until a toothpick inserted into the center comes out clean.

Place the chopped chocolate, butter, salt, and vanilla in a bowl.

In a small saucepan, heat the cream and sugar until hot but not boiling.

Pour the hot cream mixture over the chocolate and stir until smooth.

Chill in the fridge until thickened to a frosting-like consistency.

Transfer the ganache to a piping bag with a 1/4" tip or a ziplock bag with a corner cut off.

Set up a double boiler: Fill a saucepan with about 1" of water and bring to a simmer. Place a heatproof bowl over the pot, ensuring it doesn't touch the water.

Add the egg whites, sugar, and cream of tartar to the bowl. Stir constantly over low heat until the sugar dissolves and the mixture is warm, being careful not to cook the eggs.

Remove from heat and whip the mixture on high speed until stiff, glossy peaks form.

Add the vanilla and transfer the frosting to a piping bag with your preferred tip, or a ziplock bag with a 1/2" cut corner.

Poke a hole in the center of each cooled cupcake and fill with ganache.

Pipe the marshmallow frosting on top of each cupcake.

Toast the frosting with a kitchen torch for a classic s'mores look and taste. If you don't have a torch, broil the cupcakes in the oven for 1-2 minutes until golden brown.