SPRAY large baking sheet with cooking spray. Microwave sugar and corn syrup in large glass microwaveable bowl on HIGH 5 min. Stir in butter and peanuts. Microwave 3 to 4 min. or until pale golden brown. Stir in baking soda and vanilla. (Mixture will foam.) Spread onto prepared baking sheet. Cool completely. Break into pieces.

MICROWAVE chocolate in 1-cup glass measuring cup on HIGH 1 to 2 min. or until chocolate is melted when stirred. Add peanut butter; stir until melted. Dip half of each candy piece in chocolate mixture; scrape bottom against edge of cup to remove excess chocolate. Place on sheet of foil or waxed paper. Refrigerate 20 min. or until chocolate is firm.