Place a small cupcake upside down on a larger cupcake. Generously pipe buttercream frosting in between the two cakes and on top. The open star nozzle is best for this. If you don’t have a pastry bag and tip, just cut off one corner of a zip lock bag as an alternative. Cover the cupcake with a circular shaped fondant loosely, then press or crease it to make it look ghostly. Dab chocolate for eyes and mouth.