Place chocolate pieces in a large bowl. Heat heavy cream on medium high until it comes to a boil. Remove from heat and immediately pour cream over chocolate and stir until completely mixed and glossy. Allow ganache to cool before pouring over cakes as a glaze. The longer you allow the ganache to cool, the thicker it will set. Typically I stick mine in the refrigerator so it is slightly cold before whipping. For piping or frosting, allow the ganache to completely cool and set up. When you are able to spoon the ganache and it can hold its texture, it is ready for piping.