Preheat the oven to 350 degrees F. Line a muffin tin with liners. In a bowl, whisk together the graham crumbs, flour, baking powder, cinnamon and salt. Set aside.
To make the cupcakes, place the softened butter and sugar together in the bowl of your stand mixer and beat until combined and fluffy, about 5 minutes. Add in the eggs and vanilla extract, beating until combined.
Add in the dry ingredients in 2 batches, alternating with the milk and beat until just combined and smooth. Drop about 1/4 cup of batter into the liner, filling the liners 3/4 of the way full. Bake for 18 to 20 minutes, or until cupcakes are set and spring back at the touch. Let cool completely.
Once cool, scoop out the center with a serrated spoon (like a grapefruit spoon!) or knife. Fill with the ganache and frost.
Place the chopped chocolate in a bowl.
Heat the heavy cream in a saucepan until warm and bubbles just form around the edges. Pour over the chopped chocolate, then use a spoon or whisk to stir until melted and combined. Let sit until cupcakes are cool, then use a spoon to fill the ganache into the center of the cupcake.
To make the frosting, combine the egg whites, sugar and cream of tartar in a heat-proof bowl, preferably the bowl of your electric stand mixer. Place over top of a double-boiler that contains simmering water, and whisk constantly for 3 to 4 minutes until the sugar has dissolved and the egg whites are slightly warm. Immediately remove the bowl and place it on your stand mixer with the whisk attachment, beating slow at first and gradually increasing the speed to high. Beat for 6-7 minutes until glossy and thick, then beat in vanilla extract for another minute until combined.
Frost the cupcakes using a spatula. Use a kitchen torch to brown the marshmallow! [marshmallow adapted from Martha Stewart]