Place the chocolate chips in a large bowl and melt over a double boiler until all the chocolate has melted.Pour popped amaranth into the bowl with the chocolate and mix well.
Press the cardboard square against the mold and flip the mold, to have the skull facing you. Lift the mold, and carefully place the cardboard with the skull on it on a sheet tray.
Pour each bowl of icing into a disposable piping bag. Test the amount of icing that comes out before decorating your skull.Decorate your skull however you desire. The icing will take about 30 min. to set.