Heat 1/2 cup heavy cream in a 1 1/2-quart saucepan over medium-high heat. Bring to a boil. Place 6 ounces semisweet chocolate in a stainless steel bowl. Pour the boiling cream over the chocolate and allow to stand for 5 minutes. Stir with a whisk until smooth. One at a time, dip the top of each of Granny's cupcakes into the chocolate icing. Sprinkle the grated white chocolate over the icing on each cupcake, and refrigerate for 30 minutes to set the icing. Allow the cupcakes to come to room temperature for 15 to 20 minutes before serving. Yield: 18 cupcakes