Creating these delightful cupcakes is a simple yet rewarding task. Follow these steps to make your S’mores Cupcakes:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Line a cupcake tin with cupcake liners.
2. Mix Dry Ingredients: In a large bowl, sift together the all-purpose flour, sugar, cocoa powder, baking powder, baking soda, and salt.
3. Combine Wet Ingredients: In a separate bowl, whisk together the egg, buttermilk, vegetable oil, and vanilla extract until well combined.
4. Add Wet to Dry: Pour the wet mixture into the dry ingredients and mix until just combined.
5. Incorporate Boiling Water: Gradually add the boiling water to the mixture, stirring gently until the batter is smooth. This will make for a moist cupcake.
6. Fill the Cupcake Liners: Divide the batter evenly among the cupcake liners, filling them about two-thirds full.
7. Bake: Place the cupcake tin in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
8. Cool: Remove the cupcakes from the oven and allow them to cool in the tin for about 10 minutes before transferring them to a wire rack to cool completely.
9. Prepare the Frosting: While the cupcakes cool, make the marshmallow frosting. Place the egg whites, sugar, and water in a heatproof bowl over simmering water. Whisk continuously until sugar dissolves.
10. Whip the Frosting: Transfer the mixture to a mixing bowl, and using an electric mixer, beat on high speed until glossy peaks form. Stir in the vanilla extract.
11. Frost the Cupcakes: Once the cupcakes have cooled, generously frost each with the marshmallow frosting.
12. Toast the Frosting: For that iconic toasted marshmallow flavor, use a kitchen torch to carefully toast the frosting until lightly browned.
13. Add Toppings: Sprinkle crushed graham crackers and mini chocolate chips on top.

Now, your S’mores Cupcakes are ready for serving and delighting your guests!