Place peanut butter in a mixing bowl, on low speed, gradually beat in milk; scraping bowl several times. Add pudding mix and beat on low 2 minutes. Whisk in whipped topping; pour one-half of mixture into prepared pie crust. Whisk cocoa into remaining filling mixture; gently pour over butterscotch-peanut butter mixture. Smooth top. Sprinkle with cookie crumbles, if desired. Freeze until firm. Cut into eight wedges and serve while frozen.