In a heavy saucepan, over low heat, melt the chocolate chips with the marshmallows, the sweetened condensed milk and salt. Do not over cook.
Remove from heat and stir in vanilla and nuts.
Spread evenly into a waxed paper-lined 8 or 9 inch square pan.
Chill for at least 2-3 hours or until firm.
Turn fudge, peel off paper and cut into squares.
Store covered at room temperature.