I used a purchased pie crust and cooked the specified time in the oven. Let cool.
Stir together 2/3 cup sugar, 1/3 cup cornstarch and 1/2 tsp. salt. Using a whisk, beat 4 egg yolks with 2 cups of milk and one cup of heavy cream. Gradually blend milk mixture in with dry ingredients in a glass bowl. Cook in microwave (this is how I cook all my cream pies) and stir every minute and a half with the wire whisk until mixture has thickened. (Usually takes about 8-10 minutes depending on your microwave). Add 1 T. vanilla extract, 2 T. butter and 1 1/2 cups chocolate chips (I used Ghiradelli's semi-sweet). Stir until chips are melted and pour into crust. Put plastic wrap on top of pie and chill for 8 hours. Then top with whipped topping.
So creamy and delicious!! I'll be making this time and time again.