- 1 cup plus 2 tablespoons graham cracker crumbs (from 16 to 18 squares)
- 3 tablespoons sugar
- 5 tablespoons unsalted butter, melted
- 6 ounces bittersweet chocolate, roughly chopped
- 1 cup plus 1 tablespoon sugar
- 3/4 cup plus 2 tablespoons flour
- 7 tablespoons cocoa powder (not Dutch-processed)
- 3/4 teaspoon baking powder
- 3/4 teaspoon baking soda
- 1/2 teaspoon salt
- 1 large egg, room temperature
- 1/2 cup milk
- 1/4 cup vegetable oil
- 1 tsp pure vanilla extract
- 1/2 cup boiling water
- Extra chocolate or graham cracker pieces, to garnish
- 5 large egg whites
- 1 1/4 cup sugar
- 1/2 tsp cream of tartar
- 1 tsp pure vanilla extract
For the cupcakes:
Preheat oven to 350 degrees F. Line 2 standard muffin pans with 18 cupcake liners; set aside. Place the graham cracker crumbs, 2 tablespoons sugar, and melted butter in a large bowl; stir until well combined. Place 1 tablespoon of the graham cracker mixture prepared earlier into the bottom of each prepared muffin cup. Use the bottom of a small glass to pack crumbs into the bottom of each cupcake liner. Reserve remaining graham cracker mixture for topping. Place 2 teaspoons of chocolate in each muffin cup. Set pan aside.
Sift the sugar, flour, cocoa powder, baking powder, baking soda, and salt together into a large bowl. Mix these together until evenly combined. In a separate large bowl, mix together the egg, milk, oil, and vanilla. Add the liquid mixture into the flour mixture and beat on medium speed for 30 seconds. Scrape down the sides of the bowl and continue mixing on medium speed for 1 to 2 minutes. Add boiling water and stir to combine; set cake batter aside.
Transfer the muffin pans prepared earlier to oven and bake until the edges of the graham cracker mixture is golden, about 5 minutes. Remove from oven and fill each cupcake liner three-quarters full with cake batter. Sprinkle each with the remaining chocolate and graham cracker mixture. Return to oven and bake until tops are firm and a cake tester inserted in the center comes out clean, 18 to 20 minutes. Transfer muffin pans to a wire rack and let cupcakes cool in pan for 10 minutes. Remove cupcakes from pan and let cool completely.
For the frosting:
Place egg whites, sugar, and cream of tartar in the heatproof bowl of an electric mixer. Set over a saucepan with simmering water, making sure the water is not high enough to touch the bowl. Whisk constantly until sugar is dissolved and whites are warm to the touch, 3 to 4 minutes.
Transfer bowl to electric mixer fitted with the whisk attachment, and beat, starting on low speed, gradually increasing to high, until stiff, glossy peaks form, 5 to 7 minutes. Add vanilla, and mix until combined. Use immediately.
Transfer marshmallow frosting to a large pastry bag fitted with a large plain round, star, or French tip. Transfer cupcakes to a baking sheet or other heatproof surface. Pipe frosting in a spiral motion onto each cupcake. Using a kitchen torch, lightly brown the frosting, taking care not to burn the cupcake liners. Alternatively, you can also use your oven's broiler set on low for 1-2 minutes (keep an eye on the cupcakes the entire time!). Top each cupcake with a piece of chocolate or graham cracker, if desired. Serve immediately or store in an airtight container for up to 2 days.