Whisk peanut butter, corn syrup and warm water in small bowl.
Remove ice cream from packaging; place in large metal bowl. Let stand at room temperature 15 minutes to soften. Stir in peanut butter mixture, peanuts and cookie pieces. Freeze for 1 hour or until consistency of very thick oatmeal.
Stir fudge sauce in small bowl to loosen, or microwave on high power 15 seconds to thin slightly but not heat. Remove ice cream from freezer. Swirl in fudge. Freeze until firm. To serve, garnish with nuts if desired. Makes 8 servings.