1 cup white sugar
1 cup dark corn syrup
1 tablespoon vinegar
1 tablespoon baking soda
1 pound chocolate confectioners' coating

Butter a 9x13 inch baking dish.
In a medium saucepan over medium heat, combine sugar, corn syrup and vinegar. Cook, stirring, until sugar dissolves. Heat, without stirring, to 300 to 310 degrees F (149 to 154 degrees C), or until a small amount of syrup dropped into cold water forms hard, brittle threads. Remove from heat and stir in baking soda. Pour into prepared pan; do not spread. Mixture will not fill pan. Allow to cool completely.
In the microwave or over a double boiler, melt coating chocolate, stirring frequently until smooth. Break cooled candy into bite sized pieces and dip into melted candy coating. Let set on waxed paper. Store tightly covered.