Prepare crust - cool.
In 1 quart saucepan over very low heat melt 1 1/2 squares unsweetened chocolate -set aside.
In second 1 quart saucepan-mix gelatin, cornstarch and 1/4 c. sugar.
In small bowl with fork, beat egg yokes with milk, stir into gelatin mixture.
Cook over medium low heat stirring until mixture is thickened and coats the back of spoon.
Remove from heat and divide custard in half.
Into one half , stir melted chocolate and vanilla with spoon, beat smooth,
Refrigerate until it mounds when dropped from spoon.
Pour into crust, refrigerate.
Chill remaining custard until it mounds when dropped from spoon.
in small bowl. With mixer at high speed, beat egg whites in to soft peaks,
Gently sprinkle in 1/4 c. sugar, beating until sugar is dissolved, gently fold whites,and rum into chilled custard.Pour as much custard mixture as crust will hold into crust.Refrigerate pie a few minutes,Then pour the rest of mixture on top, refrigerate until set.
Garnish pie with whipped cream.
Shave the remaining 1/2 square of chocolate and sprinkle on top of pie