Chocolate Truffle S'mores Cupcakes

Preparation

To prepare the cupcakes, start by making the boxed cake mix according to the package directions, including preheating the oven at the listed temperature.
Place 18 paper liners into a cupcake pan and spray them with nonstick spray. Fill each liner about 2/3 full with the prepared cake batter. Bake for about 20 minutes, until the cupcakes are just under-baked, so the top appears baked, but they're still a little soft in the center. Push a chocolate truffle into each center until the top of the truffle is almost even with the top of the cupcake. Let cool.
Put the chocolate frosting into a pastry bag and pipe a swirl onto each cupcake.
To prepare the topping, whip together the egg whites, sugar, and tartar in a metal mixing bowl. Place the mixing bowl over a pot of steaming water and whisk until the mixture reaches 160°F, as measured with a kitchen thermometer.
Transfer the mixture to the bowl of a stand mixer, then add the vanilla extract and whip until soft peaks form. When finished, spoon a small amount of the topping onto each cupcake. Optional: Use a small kitchen torch, like you would for crème brûlée, to lightly toast the topping.
To prepare the garnish, break up the chocolate bars into their individual squares and top each cupcake with a chocolate piece. Add a few mini teddy bear graham crackers overtop.