In double boiler, blend together:
1/2 cup sugar
1/3 cup cornstarch
1/2 tsp. salt
3 cups milk
4 beaten egg yolks
2 squares unsweetened chocolate
Stir frequently until thickened, scraping sides and bottoms carefully to incorporate cornstarch fully.
Pour into bowl and stir in 1 tsp. vanilla.
Cover with plastic wrap up against filling to avoid a "skin" , and refrigerate until cool.
Pour into pre baked 9 in. pie crust, and top with cream and shaved chocolate.