2 (1-ounce) squares unsweetened chocolate
1/3 cup butter or margarine
¾ cup sugar
1/3 cup all-purpose flour
3 cups whipping cream, divided
2 egg yolks, lightly beaten
1 baked 9-inch pastry shell
2 tablespoons powdered sugar
Garnish chocolate shavings
Place chocolate and butter in top of a double boiler; bring water to a boil. Reduce heat to low; cook until chocolate and butter melt.
Add sugar and flour; stir well. Gradually stir in 2 cups of whipping cream. Cook, stirring constantly, 20 minutes or until mixture thickens. Gradually add one-fourth of hot mixture into egg yolks. Add to remaining hot mixture, stirring constantly. Cook until mixture thickens and reaches 160 degrees. Remove from heat. Cover tightly with plastic wrap; cool to room temperature, and spoon mixture into pastry shell. Cover and chill 2 hours.
Beat remaining 1 cup whipping cream at medium speed with an electric mixer until foamy; gradually add powdered sugar, beating until soft peaks form. Spread whip cream on pie. Garnish, if desired.