In heavy gauge saucepan, combine marshmallow cream, sugar, evaporated milk, butter and salt. Bring to a FULL ROLLING BOIL over medium heat, stirring constantly. Remove from heat. Add Mint-Chocolate chips; stir until chips are melted and mixture is smooth. Add nuts and vanilla extract. Pour into foil-lined 8-inch square pan. Chill until firm, about 2 hours. Cut into 1-inch squares.