Step 1

Line a 15x10x1-in. pan with foil. Grease the foil with 1 teaspoon butter; set aside.

Step 2

In a heavy saucepan, combine the sugar, corn syrup, water, vinegar and remaining butter. Bring to a boil over medium heat, stirring occasionally. Cover and cook for 3 minutes to dissolve any sugar crystals.

Step 3

Uncover; cook, without stirring, until a candy thermometer reads 300° (hard-crack stage). Remove from the heat. Pour into prepared pan without scraping the saucepan; do not spread mixture.

Step 4

Cool for 1-2 minutes or until candy is almost set. Using a sharp knife, score into 1/2-in. squares; cool completely. Break squares apart. Store in an airtight container.