In a heavy saucepan, combine the sugar, corn syrup and vinegar.

Cook over medium heat, stirring constantly, until sugar dissolves.

Cook without stirring until the temperature reaches 300° (hard-crack stage) on a candy thermometer. Do not overcook.

Remove from the heat and quickly stir in baking soda.

Pour into a buttered 13×9 in pan. Do not spread candy; mixture will not fill pan.

When mixture is cool, break into bite sized pieces. Dip into melted chocolate; place on waxed paper until the chocolate is firm.

Store candy in an airtight container.