Combine the sugar and cornstarch in a heavy 2-quart saucepan.
Stir in the corn syrup, water, salt, and butter.
Cook over medium heat, stirring constantly, until the mixture boils and the sugar is dissolved.
Continue cooking without stirring until candy thermometer reaches to 256° to 260°, or until it reaches between firm and hard ball candy stage (mixture will form a flexible ball when drizzled in cold water).
Remove from the heat After boiling has ceased, stir in vanilla.
Pour onto lightly greased pan.
Let stand until cool enough to handle. Wear gloves or grease hands with oil.
Pull the taffy with greased hands.
Cut into 1-inch pieces and wrap the candy pieces in waxed paper.