LINE 8-inch square pan with foil, with ends of foil extending over sides of pan. Set aside.
MICROWAVE chocolate and milk in microwaveable bowl on HIGH 2 to 3 min. or until chocolate is almost melted, stirring after 2 min.
STIR until chocolate is completely melted. Blend in vanilla.
SPREAD into prepared pan.
REFRIGERATE 2 hours or until firm. Use foil handles to lift fudge from pan before cutting to serve.