In a heavy medium saucepan combine the 1 cup whipping cream, chocolate pieces, butter and sugar. Cook over low heat, stirring constantly, until chocolate is melted (about 10 minutes). Remove from heat.
Gradually stir half of the hot mixture into beaten egg yolks. Return egg mixture to chocolate mixture in saucepan. Cook over medium-low heat, stirring constantly, until mixture is slightly thickened and begins to bubble (about 5 minutes). Remove from heat. (Mixture may appear to separate.)
Stir in the 3 Tbsp. creme de cacao or 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 cooled chocolate mixture with an electric mixer on medium to high speed for 2 to 3 minutes or until light and fluffy.
Spread caramel ice cream topping in bottom of baked pastry shell. Sprinkle pecans or almonds evenly over caramel. Carefully spread filling into pie shell.
Cover and refrigerate pie for 5 to 24 hours. To serve, top with whipped cream and if you like, garnish with chocolate curls.