1 9-inch baked pie shell
1 cup granulated sugar, divided
1 envelope unflavored gelatin
1/2 tsp salt
1 1/3 cups water
2 squares (1-oz each) unsweetened chocolate, melted
3 eggs, separated
1 tsp vanilla
1/4 tsp cream of tartar
1/2 cup chilled whipping cream
Stir together the gelatin, salt, and 1/2 cup of the granulated sugar; stir in the water and chocolate. Cook the mixture over medium heat, stirring constantly, until blended. Remove from the heat.
Beat the egg yolks lightly; stir in the chocolate mixture slowly into the egg yolks.
Return the mixture to the saucepan and cook over medium heat, stirring constantly, just until the mixture comes to a boil. Place the pan in a bowl of ice water; stirring occasionally, until the mixture mounds slightly when dropped from a spoon. Stir in the vanilla.
Beat the egg whites and cream of tartar until foamy. Beat in the remaining half cup of sugar, 1 tablespoon at a time; continue beating until stiff and glossy. Do not underbeat!
Fold the chocolate mixture into the meringue.
Beat the whipping cream in a chilled bowl until stiff. Fold into the chocolate meringue.
Pile the filling into the pie shell. Refrigerate at least 3 hours or until set.