1. In a medium saucepan, combine the flour, salt, granulated sugar, and spices.
2. Gradually add the milk, stirring constantly.
3. Bring the mixture to a boil and cook over medium heat, stirring continuously until it thickens. Continue cooking for another minute while stirring occasionally.
4. Remove from heat and gradually stir some of the hot mixture into the beaten egg yolks. Then return everything to the saucepan.
5. Simmer over low heat, stirring occasionally, for another two minutes.
6. Remove from heat, and blend in the peanut butter, unsalted butter, and vanilla essence.
7. Pour the filling into the baked pie crust after it has cooled to room temperature.
8. Chill the pie for at least three hours or until it sets.
9. Just before serving, whip the powdered sugar and heavy cream to soft peaks. Top the pie with whipped cream once cooled.
10. Garnish with chopped peanuts or chocolate shavings if desired.

Tips:

• Swap the regular pie crust with graham cracker or chocolate cookie crust for a different flavor.
• Add melted chocolate into the peanut butter mixture before filling the crust for a layered look.
• For added flavor, add sliced bananas to the crust before pouring in the filling.