Dark Chocolate Fudge

3 c semi-sweet chocolate chips
14 oz sweetened condensed milk
1/8 ts salt
1 c chopped walnuts
1 1/2 ts vanilla

in heavy saucepan, over low heat, melt chips with sweetened condensed milk and salt. Remove from heat; stir in walnuts and vanilla. Spread evenly into wax paper-lined 8 or 9-inch square pan. Chill 2 hours or until firm. Turn fudge onto cutting board; peel off paper and cut into squares. Store loosely covered at room temperature.