Empress frosting

INGREDIENTS:
    1/3 c  Half & half
    1/2 c  butter, cut up
      2 tb Sugar
  1 1/2 c  Ghirardelli Sweet Ground
           -chocolate
      1 ts vanilla
 
  DIRECTIONS: In 2 quart heavy saucepan, heat half & half with butter
  and sugar, stirring until blended. Add Ground chocolate, mixing with
  wire whip until smooth. Heat on medium low until mixture is thick and
  shiny and runs off the spoon like syrup and the first bubble appears
  on the surface (160-F). Do not boil or overcook frosting. Cool 5
  minutes, then add vanilla. Place pan of frosting in bowl holding a
  tray of ice cubes and some water. Beat slowly with a spoon until
  frosting holds a shape. Frost cake; refrigerate if necessary to firm
  frosting.
  
  Source: Recipes from Ghirardelli chocolate Company of San Francisco;
  recipe on box of "Sweet Ground chocolate and Cocoa"
  
  From: Sallie Austin