Beat together the confectioners' sugar and peanut butter until the mixture
is crumbly; set aside.
In a large, heavy saucepan, combine 2/3 cup sugar and 2 cups milk; heat
to scalding or until bubbles start to form on the bottom. Do not let it boil.
Meanwhile, in a medium bowl, beat the egg yolks to mix; blend in 3 tablespoons
cornstarch, flour and salt. Stir to make a paste.
Whisk in the remaining 1 cup cold milk, whisking until the mixture is smooth.
Pour in some of the hot milk mixture, stirring to combine.
Add mixture in bowl to the milk in the saucepan. Cook over medium-low heat,
stirring constantly, until the mixture bubbles up in the center.
Add the butter and 1 teaspoon vanilla extract. Remove from heat and let
Heat oven to 350 degrees F.
Sprinkle 2/3 of the crumbly peanut butter mixture into the bottom of the
baked (and cooled) pastry shell. Pour the cooled custard mixture over the top.
In a large mixer bowl, beat the egg whites, cream of tartar and remaining
1 teaspoon vanilla extract until stiff peaks form.
Gradually, while beating, add the remaining 4 tablespoons sugar and remaining
3 tablespoons cornstarch. Continue beating until whites are very think and glossy.
Spread on top of pie. Sprinkle the remaining peanut butter mixture on top.
Bake for 12 to 15 minutes; watching carefully, or until the meringue is
golden brown; cool.