In a large mixing bowl, beat until easily stirred
Then beat in the peanut butter and unsifted icing sugar.
In a small bowl, beat whipping cream until soft peaks form
Gradually beat in the sifted icing sugar and vanilla
Stir a third into peanut butter mixture. Gently fold in remaining cream, just until mixed.
Pour into the pie shell. Smooth top and refrigerate.
For topping, stir whippimg cream and chocolate often for about 5 minutes, in a double boiler over hot water. Or microwave, uncovered, on medium power, from 2 to 3 minutes. Then stir until smooth.
Cool until lukewarm. Pour over pie and spread to pastry edge. Refrigerate until topping is firm, at least 2 hours. Cover with plastic wrap once topping has set.
Refrigerate for up to 2 days. Or freeze.