PREHEAT oven to 350°F. Mix flour and brown sugar in medium bowl. Cut in butter with pastry blender or 2 knives until mixture resembles coarse crumbs. Press crumb mixture firmly onto bottom of foil-lined 13x9-inch baking pan. Bake 15 minutes.
SPRINKLE pecans and coconut over crust; cover with condensed milk. Bake an additional 25 minutes or until coconut is lightly browned. Cool in pan on wire rack.
MICROWAVE caramels and milk in medium microwavable bowl on HIGH 2 minutes or until caramels are completely melted and mixture is well blended, stirring after each minute. Drizzle over dessert; sprinkle with chocolate chunks. Cool completely. Cut into 36 bars to serve.