Line 8-inch square pan with foil, with ends of foil extending over sides. Melt 4 oz. chocolate in microwave as directed on package; spread onto bottom of prepared pan. Refrigerate 10 min. or until firm.
Microwave remaining chocolate and milk in same bowl on HIGH 2 to 3 min. or until chocolate is almost melted; stir until completely melted.
Add cream and vanilla; mix well.
Spread over chocolate layer in pan.
Refrigerate 2 hours or until firm. Use foil handles to lift fudge from pan before cutting into squares.
