Chocolate-Caramel Cookie Bars

Heat oven to 350ºF. Line 13x9-inch pan with foil, with ends of foil extending over sides; spray with cooking spray. Beat cake mix, butter and egg with mixer until blended. (Dough will be stiff.) Press 2/3 of the dough onto bottom of prepared pan. Microwave peanut butter, caramels and water in microwaveable bowl on HIGH 2 min.; stir until caramels are completely melted and mixture is well blended. Pour over dough in pan. Pinch small pieces of remaining dough between your fingers; place on caramel layer. Sprinkle with chocolate and nuts. Bake 25 to 30 min. or until centre is almost set. Cool completely. Use foil handles to lift dessert from pan before cutting into bars. n