1. Mix cookie crumbs and butter; press onto bottom of 13 x 9-inch pan. Freeze until ready to use. Microwave peanut butter in small microwaveable bowl on High for 1 minute, then stir. Swirl peanut butter into ice cream; spread over crust. Freeze 30 minutes.
2. Microwave Cool Whip and chocolate in medium microwaveable bowl on High 1-1/2 to 2 minutes or until chocolate is completely melted and mixture is well blended, stirring after each minutes.
3. Spread Cool Whip mixture over ice cream layer; top with nuts. Freeze for 4 hours. Remove from freezer 10 minutes before serving; let stand at room temperature to soften slightly before cutting. Freeze leftovers.