Melt butter in saucepan. Stir in sugar, milk, corn syrup, and salt. Bring to a boil--Reduce to very low heat. Cook, Stiring almost constantly 25 - 30 minutes or until hard ball stage in cold water. Remove from heat. Stir in vanilla and pecans. Drop in 1 1/2 inch wide mounds from spoon onto buttered foil. With spoon spread small amount of melted chocolate over each candy. Let stand until firm. Wrap each turtle separately in plastic wrap.