PREHEAT oven to 350°F. Place chocolate and butter in large microwavable bowl. Microwave on HIGH 2 min. or until butter is melted. Stir until chocolate is completely melted. Add sugar; stir until well blended. Mix in eggs. Add flour; mix well. Stir in pecans. Spread into greased foil-lined 13x9-in. baking pan.
BAKE 30 to 35 min. or until toothpick inserted in center comes out with fudgy crumbs. DO NOT OVERBAKE.
MEANWHILE, place caramels and milk in microwavable bowl. Microwave on HIGH 2-1/2 min., stirring after 1 min. Stir until caramels are completely melted and mixture is well blended. Gently spread over brownie in pan; sprinkle with chocolate chunks. Cool in pan on wire rack. Lift out of pan onto cutting board. Cut into 36 bars.