Preheat the oven to 350 degrees. Line two cupcake pans with paper liners.
In a small mixing bowl, combine the graham cracker crumbs, sugar and melted butter; mix well with a fork. Drop about 1 tablespoon of the graham cracker mixture in the bottom of each cupcake liner and press down to line the bottom. (Note: I use the bottom of a dry measuring cup.) Bake for 5 minutes. Remove from the oven, and maintain the oven temperature.
In a small bowl, combine the cocoa powder and hot water; whisk until smooth. In a medium bowl combine the flour, baking soda, baking powder, and salt and whisk to blend. Combine the butter and sugar in a medium saucepan set over medium heat. Cook, stirring occasionally, until the mixture is smooth and the butter is completely melted. Transfer the mixture to the bowl of an electric mixer and beat on medium-low speed until the mixture is cool, about 4 to 5 minutes. Add the eggs one at a time, mixing well after each addition and scraping down the sides of the bowl as needed. Blend in the vanilla and then the cocoa mixture until smooth. With the mixer on low speed, add the flour mixture in three additions alternating with the sour cream, beginning and ending with the dry ingredients and mixing each addition just until incorporated.
Divide the batter evenly between the prepared liners, filling each about ¾-full. Bake until a toothpick inserted in the center comes out clean, about 18 minutes, rotating the pans halfway through baking. Let cool in the pan about 5 to 10 minutes, then transfer to a wire rack to cool completely.
To make the frosting, combine the egg whites, sugar and cream of tartar in a heat-proof bowl. Set bowl over a pan of gently simmering water. Heat the mixture, whisking frequently, until it reaches 160 degrees with an instant-read thermometer. Transfer the mixture to the bowl of an electric mixer fitted with the whisk attachment. Whisk starting at low speed and gradually increasing to medium-high speed until stiff, glossy peaks form. Mix in the vanilla until combined. Transfer the frosting to a pastry bag fitted with a decorative tip. Pipe as desired onto each cupcake and then brown frosting with a kitchen torch. Garnish with chocolate and graham cracker segments (optional).