Soften gelatin in cold water. Melt chocolate chips in the top of a double boiler or in a bowl in the microwave. Stir until smooth. Set aside to cool.

Combine 1/2 cup sugar, cornstarch, and salt in a saucepan. Blend together milk and egg yolks, stir into sugar mix. Cook over medium heat, stirring constantly, just until mixture boils. Remove 1 cup of custard, and combine with chocolate: spread into baked pie shell. Stir softened gelatin into remaining hot custard mix. Stir in rum. Place pan in a bowl of ice water, or refrigerate. Stir occasionally, until mixture mounds slightly when dropped from spoon. Combine chocolate & the reserved custard mix. Pour into baked pie shell.

Stir softened gelatin into remaining hot custard mix. Stir in rum. Place pan in a bowl of ice water, or refrigerate. Stir occasionally, until mixture mounds slightly when dropped from spoon.

Beat egg whites and cream of tartar until foamy. Beat in 1/3 cup sugar, 1 tablespoon at a time, and continue beating until stiff and glossy. Do not underbeat. Fold in chilled custard. Spread over chocolate mixture. Chill at least 3 hours or until set.