Allow the cupcakes to cool. Place your chopped chocolate in a medium heat-safe bowl.
Bring your heavy cream up to a boil in a medium saucepan, keeping an eye on it so it doesn't boil over.
Pour the heavy cream over the chopped chocolate and cover the bowl with plastic wrap, let it set for 5 minutes.
Using a rubber spatula start stirring the chocolate by making small circles in the middle of the bowl and slowly stirring, making your way to the outside of the bowl until all the heavy cream is incorporated.
Allow the ganache to set for 15 minutes.
Using your apple corer remove about one inch of the center of each cupcake.
Pour your cooled ganache into the piping bag and cut off the bottom of the bag.
Fill each cupcake with the ganache leave a small gap on the top for the graham crackers.
Fill each cupcake hole to the top with the graham cracker crumbs.
Break the graham crackers and chocolate bars into one-inch pieces.
Put the cupcakes onto a sheet pan and top each one with a marshmallow then place the cupcakes under the broiler until they are golden brown.
While the marshmallows are still warm press down on the marshmallows to make them flat then press one piece of the chocolate and graham crackers into the top of each cupcake making sure you reach the cupcake so they don't fall out.