In top of double boiler, melt chocolate over boiling water, stirring occasionally.
Remove from heat; stir in sweetened condensed milk, salt, vanilla, and nuts.
Spread mixture evenly into waxed-paper-lined 8x8-inch baking pan.
Chill for 2 hours or until firm.
Turn fudge onto cutting board; peel off paper and cut into squares.
Tightly cover any leftovers