This is similar to Lori D's pie:

8 oz. cream cheese, softened
8 oz. creamy peanut butter
8 oz. Cool Whip
1/4 C. powdered sugar
Chocolate syrup or fudge sauce
Large graham cracker crust

Beat the cream cheese & peanut butter 'til smooth. Add powdered sugar and beat 'til smooth. Fold in the Cool Whip.

If desired, pour a thin layer of chocolate syrup/fudge onto the bottom of the pie crust. Pour in pie filling, and chill at least 2 hours. If desired, drizzle chocolate sauce over the filling, or pour another thin layer of fudge sauce (which will set up better than the chocolate syrup) and chill for at least another 30 minutes.

This filling is very versatile -- I've used it between cake layers & for cream puff filling.