Whip cream cheese and powdered sugar in large bowl until light and fluffy. Add peanut butter and milk. Beat well. Stir in vanilla and nuts. Fold in Cool Whip and set aside.
Take baked pie shell and generously spread hot fudge in and up the sides of the pie shell. Pour pie mixture into pie shell. Garnish with remaining hot fudge, extra Cool Whip or extra nuts, whatever you desire.