Heat oven to 350°F. Lightly spray 13x9-inch pan with baking spray with flour (do not use dark or nonstick pan). In large bowl, mix cake mix, butter, milk and 1 egg with spoon until dough forms. Spoon into pan. Place plastic wrap on dough; press evenly in pan. Remove plastic wrap. Sprinkle dough with peanut butter chips and peanuts.