Prepare cupcakes according to package directions.
When cooled, remove center of cupcake with a small paring knife, apple corer or tool made for this purpose.
Fill pastry bag or zip type bag with marshmallow fluff. Pipe the marshmallow fluff in center hole of cupcake.
Frost the cupcakes with a generous amount of chocolate frosting. Place graham cracker crumbs in small plate and roll edges of frosted cupcake in graham cracker crumbs. Unwrap mini chocolate bars and place one in the center of each cupcake.