In a mixing bowl, cut the peanut butter into the powdered sugar till crumbly. Set aside.
For the filling, in a medium or large saucepan, combine the sugar and cornstarch. Add milk all at once. Cook and stir till bubbly. Cook 2 minutes more. Remove from heat and gradually stir about 1 cup of the hot mixture into the eggs. Return all to saucepan. Cook till nearly bubbly, but do not boil. Reduce the heat. Cook and stir the mixture for 2 minutes more. Stir the butter or margarine and vanilla into the mixture.
Sprinkle the baked crust with half of the peanut butter mixture. Mound the filling on top. Cover; chill 1 hour.
In a mixing bowl, beat the whipping cream just till stiff peaks form (tips stand straight). Spread whipped cream over pie. Sprinkle with remaining peanut mixture. Chill till serving time (at least 2 hours). Store leftovers in the refrigerator. Makes 8 servings. From Rosie's Diner in Rockford, MI Recipe printed in Midwest Living, April 1993