Preparation:
1. Thoroughly combine sugar, cocoa, corn syrup, vinegar and salt in a heavy 4-quart saucepan.
2. Add butter; cook, stirring constantly, over low heat until sugar dissolves and mixture comes to a boil.
3. Gradually add evaporated milk; cook and stir over low heat until mixture registers 265 F. on candy thermometer (hard-ball stage) or until small amount of syrup dropped into very cold water forms a hard ball.
4. Stir into popped corn.
5. Butter hands; quickly roll large spoonfuls of mixture into 4-inch balls. | 