LINE 9-inch square pan with foil, with ends of foil extending over sides; set aside. Mix baking crumbs and margarine; press onto bottom of prepared pan.

MELT 4 chocolate squares as directed on package. Beat cream cheese in medium bowl with mixer until creamy. Gradually add sweetened condensed milk, beating well after each addition. Blend in melted chocolate. Whisk in Cool Whip; spoon over crust. Freeze 3 hours or until firm. Meanwhile, make chocolate curls from remaining chocolate square; refrigerate until ready to use.

REMOVE dessert from freezer 15 min. before serving; let stand at room temperature to soften slightly. Use foil handles to remove dessert from pan before cutting into squares to serve. Top with chocolate curls.