Preheat your oven to 350°F and line a cupcake tin with liners. Set aside.
In a large bowl, sift together the flour, baking soda, cocoa, and salt. Set aside.
In another bowl, combine both sugars and the butter. Use an electric mixer on medium-high speed to cream until light and fluffy. Add the eggs one at a time, beating for 30 seconds after each addition. Stir in the vanilla extract until well mixed.
Add half of the dry ingredients and ½ cup of milk to the sugar mixture. Mix on low speed until combined. Repeat with the remaining dry ingredients and ½ cup milk, mixing on low until well blended.
Fill the cupcake liners ⅔ full with the batter. Bake for 15-18 minutes, rotating halfway through, until a toothpick inserted into the center comes out clean.
Let the cupcakes cool in the pans on wire racks for 25 minutes, then remove them from the pans and place directly on the racks to cool completely (about one hour).
Icing
In a medium bowl, use an electric mixer to cream the butter. Gradually add the milk and icing sugar, alternating between them, and beat on low speed until combined. Add the cocoa powder and beat on low speed for another minute. Add the vanilla extract and mix on medium-high speed for 3-4 minutes until light and fluffy.
Transfer the frosting to a pastry bag with a tip (or use a Ziploc bag with the corner snipped) and frost the cupcakes. A Wilton 1M tip was used in this recipe.
Garnish
Drizzle marshmallow sauce over the frosted cupcakes, and sprinkle with mini chocolate chips and mini marshmallows. Top each cupcake with a piece of graham cracker and a piece of Hershey’s chocolate bar. Drizzle Hershey’s chocolate sauce on top.
This recipe makes 18 regular-sized cupcakes or 10 jumbo cupcakes.