Stir semi-sweet and white chocolate chips together in a large bowl. In small saucepan over medium-high heat bring cream almost to a boil; pour over the chips. Whisk the cream/chocolate mixture until chips are melted and mixture is smooth. Add confectioners sugar and whip with an electric mixer until icing is again smooth. Mixture will be thin. Place in refrigerator.
When cooled and thickened, about 90 mins, again beat with electric mixer until fluffy and light brown in color. Frost cake; store in fridge until ready to eat.