1 cup sugar
1 cup white corn syrup
1 tbsp. vinegar
1 1/2 tbsp. baking soda
1 (6 oz.) pkg. semi-sweet chocolate chips

Combine sugar, syrup and vinegar in large saucepan. Cook to a hard-crack stage (300°F to 310°F). Turn off heat and add baking soda, mixing quickly. Pour immediately into a greased 1 x 7 x 1 1/2-inch pan. Cool; then invert on a tray. Spread with melted chocolate. Break into chunks.

Note: A candy thermometer is recommended.