Combine milk, butter, sugar and salt. Bring to a vigorous boil, stirring often; then reduce heat and simmer 6 minutes.
Meanwhile place remaining ingredients (except pecans) in a large bowl. Gradually pour boiling syrup over the chocolate-marshmallow mixture and beat until chocolate is melted. Stir in nuts. Pour into buttered pans and store in a cool place several hours to harden before cutting in squares.