How to make it :
To make the crust:
Place rack in center of the oven and preheat the oven to 325 F, line cupcake tins with 16 cupcake liners and set aside.
In a small bowl, combine graham cracker crumbs, sugar, and melted butter and mix well with a fork.
Press about 1 1/2 Tablespoon of the mixture into the bottom of each cupcake liners and bake 6 minutes, then set aside to cool.
To make the cupcakes:
In a large bowl combine cocoa, sugar, flour, baking powder, baking soda, and salt.
Add oil, milk, egg, and vanilla. Beat for 2 minutes with a hand-held electric mixer on medium speed, then add boiling water and beat to combine (batter will be thin). Divide batter evenly between cupcake liners over the crust (it should be 3/4 full)
Bake until a toothpick inserted into the center comes out clean, about 20-25 minutes. Set aside to cool in pan, then using a sharp knife or cupcake corer hollow out the centers of each cupcake(cut the top of each center and save for later to place it back onto the filling).
To make marshmallow filling:
In a heatproof bowl over a pot of simmering water whisk together egg whites, sugar and cream of tartar, until sugar dissolves (be careful, the water shouldn’t touch the bottom of the bowl). Continue whisking over simmering water until egg mixture is warm to touch, then remove from heat and continue beating with the mixer until still peaks form. At the end add vanilla and mix well.
Transfer the filling to a piping bag with round tip or use the plastic bag and cut off the corner and fill the cupcakes. Place back the tops from centers of cupcakes.
To make the ganache:
On a low heat in a small sauce pan melt chopped milk chocolate with 1/2 Tablespoon vegetable oil, stirring until it’s completely smooth. Remove from heat and add cold heavy whipping cream, stir well until it’s evenly combined. Using a spoon spread the ganache onto the cupcakes. If the ganache is the too runny place it in the fridge briefly to set to top the cupcakes.
Store in the fridge.