Line a 8" square pan with foil extends over sides of pan; butter foil and set aside. In a saucepan, combine sugar, melted margarine, and milk. Bring to a boil over medium heat, stirring constantly. Boil five minutes, stirring constantly. Remove from heat. Add marshmallow cream and chocolate chips; blend until smooth. Stir in walnuts and vanilla extract. Pour into prepared pan. Chill for two hours, or until firm. Turn fudge onto cutting board. Peel off foil and cut into squares.
You may use peanut butter, vanilla, or butterscotch chips in place of the milk chocolate chips. This recipe doesn't half well.