Prepare pie shell; cool. Mix gelatin and water in small bowl; allow to soften. Slightly beat egg yolks with vanilla in mixing bowl; set aside. Combine 3/4 cup sugar, cocoa and salt in saucepan; stir in milk. Cook and stir until mixture comes to a full boil; add gelatin and return to boil. Remove from heat; immediately whisk into beaten egg yolks. (Mixture will thicken slightly.) Cool; chill until mixture mounds from a spoon, stirring occasionally. Whip cream until stiff. Fold into chocolate or fold whipped topping into chocolate. Beat egg whites with remaining 1/4 cup.