Foolproof Chocolate Fudge

In heavy saucepan, over low heat, melt chocolate chips with sweetened condensed milk and salt. Remove from heat; stir in nuts (optional) and vanilla.
Spread evenly into wax-paper-lined 8- or 9-inch square pan. Chill 2 hours or until firm.
Life fudge out of pan and place onto cutting board; peel off paper and cut into squares. Store covered in refrigerator.