• In a medium, heavy saucepan combine 1 cup of the whipping cream, chocolate, butter and sugar. Cook over low heat, stirring constantly, until the chocolate melts (about 10 minutes). Remove from heat. Gradually stir half of the hot mixture into the beaten egg yolks. Return the egg mixture to the chocolate mixture in the pan. Cook over medium-low heat, stirring constantly, until the mixture is slightly thickened and begins to bubble (about 5 minutes). Remove from heat (the mixture might appear a bit curdled). Stir in the remaining 3 tablespoons of whipping cream. Place the saucepan in a bowl of ice water, stirring occasionally, until the mixture stiffens and becomes hard to stir (about 20 minutes).
• Transfer the chocolate mixture to a medium mixing bowl. Beat the chocolate mixture with an electric mixer on medium to high speed for 2 to 3 minutes or until light and fluffy. Spread the filling in the baked pie crust. Cover and chill for 5 to 24 hours.

ADD WHIPPED CREAM TO SERVE:

• In a medium bowl, combine the cream, powdered sugar and vanilla. Use an electric hand mixer to mix until stiff peaks form (2 to 4 minutes). Spread the whipped cream on top of the chilled pie. Slice and serve.