Place chocolate squares in a small, microwave-safe bowl. Microwave on high 2 minutes. Set aside. Sprinkle gelatin over boiling water and set aside to soften.
In a large glass or metal bowl, beat egg whites until soft mounds form. Gradually add sugar, continuing to beat until whites are stiff and glossy. Beat in corn syrup and vanilla extract. Gently mix in chocolate and gelatin mixture.
Pour mixture into pastry shell. Chill at least 2 hours before serving. Garnish with whipped cream and chocolate sprinkles if desired.