Nutella Buttercream Frosting

"- This recipe will make enough frosting to generously frost 24 cupcakes or one 9 inch layer cake. - You can easily adjust the consistency of this recipe by simply adding in more heavy cream or milk. - Covered and refrigerated frosting can be stored for up to three days. Simply bring it to room temperature and beat with an electric mixer until smooth. You may need to add a couple of teaspoons of heavy cream or milk to revive the consistency. - Recipe edited 7/1/12: Due to several readers having issues with the thickness of the frosting, we have adjusted the amount of confectioners' sugar to 1.5 pounds. The thickness of the Nutella Buttercream will also depend on the amount of heavy cream that is added...."