1. Preheat the oven to 350°F. Line a 12-cup muffin tin with cupcake liners and then set aside while you prep the graham cracker mixture.
2. In a medium-sized bowl, combine the graham cracker crumbs, salt, and melted butter together. Stir to combine until the mixture takes on the texture of wet sand. Evenly divide the graham cracker mixture into the wells of each cupcake liner, about a tablespoon and a half. Then gently press the mixture tightly into the bottom of the liner.
3. Bake the graham cracker crust for 10 minutes. Then set it aside to cool down while you make the chocolate cupcake batter.
4. In a large bowl, combine the flour, brown sugar, cocoa powder, baking powder, baking soda, and salt together. Whisk the dry ingredients well to thoroughly combine. Then add in the oil, egg, buttermilk, black coffee, and vanilla extract. Whisk the mixture together until the batter is fully incorporated. The batter should be somewhat runny.
5. Evenly divide the batter into the cupcake liners directly on top of the graham cracker crust, leaving a little room at the top. 
6. Bake the cupcakes for 20-22 minutes or until a toothpick inserted into the center comes out clean. Then allow the cupcakes to cool down for 10-15 minutes before you fill with the Nutella® and frost.
7. Use a knife or the bottom of a pastry tip to cut out some of the center of each cupcake. You can save the excess cupcake bits or discard. Then place the Nutella® into a pastry bag or ziplock bag. Fill each cupcake center with the Nutella® hazelnut spread, just until you reach the top. Then set aside while you prepare the frosting.

For the marshmallow frosting:

1. Fill a small saucepan with a few inches of water and bring to a simmer. Using a small, heatproof bowl, place the egg whites, sugar, and salt into the bowl. Place the bowl over the saucepan, creating a double boiler- make sure the water in the saucepan is not touching the bottom of the bowl.
2. Continuously whisk the mixture together until the sugar dissolves and the mixture goes from thick to thin, about 5-6 minutes. As you continue to stir, look for the mixture to get somewhat frothy and warm. Carefully, test the mixture by dipping a finger in, you should feel no sugar granules when rubbing between your fingers.
3. Turn off the heat and remove the small bowl from the top. Stir in the vanilla bean paste/vanilla extract, whisk to fully combine.
4. Beat the mixture: Add the meringue into the bowl of a stand mixture or use a handheld mixer; beat the meringue on high speed until fluffy with stiff peaks, about 5-7 minutes. Lift the beater and look for the meringue to stand tall without weeping. 
5. Use an offset spatula to spread or a pastry bag to pipe the marshmallow frosting onto the cupcakes. Serve as is or use a kitchen torch to lightly toast the meringue, as pictured. Enjoy!