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 2-3 minutes, or until chocolate is almost melted, stirring 2 minutes.
Stir until chocolate is completely melted. Blend in vanilla.
Spreqd into prepared pan.
Refrigerate 2 hours or until firm. Use foil handles to lift fudge from pan before cutting to serve.