Preheat oven to 350°.

Sprinkle peanut butter chips in pie shell.
Melt butter in sauce pan. Stir in cocoa.
Cook until cocoa is dissolved, stirring constantly.
Add condensed milk and wter. Whisk until blended.
Stir in egg and vanilla.
Pour into pie shell and bake for 30 minutes or until edge is set.
Cool slightly and garnish with whipped topping or whipped cream.