Classic Chocolate Cream Pie
["2 1/2 blocks (2 1/2 oz.) Hershey's unsweetened baking chocolate, broken into pieces", "2 c. milk", "1 1/3 c. sugar", "3 Tbsp. flour", "3 Tbsp. cornstarch", "1/2 tsp. salt", "3 egg yolks", "1 c. milk", "2 Tbsp. butter or margarine", "1 1/2 tsp. vanilla", "3 egg whites (room temperature)", "1/4 tsp. cream of tartar", "6 Tbsp. sugar", "9-inch pastry crumb crust"]
["Bake pastry shell; set aside."]
["blocks", "milk", "sugar", "flour", "cornstarch", "salt", "egg yolks", "milk", "butter", "vanilla", "egg whites", "cream of tartar", "sugar", "pastry"]