In medium saucepan, mix sugar, cocoa and salt; stir in water. Cook over medium heat, stirring constantly, until mixture boils; boil and stir 2 minutes.
Add milk; stir until well blended. Cook, stirring often, until hot.
DO NOT BOIL. Remove from heat; stir in vanilla. Beat with whisk until foamy. About six 6-ounce servings.
SINGLE SERVING: Combine 1 heaping teaspoon HERSHEY'S Cocoa, 2 heaping teaspoons sugar and dash salt in mug. Add 2 teaspoons milk; stir until smooth. Stir in 1 cup hot milk; serve.
MICROWAVE SINGLE SERVING: In microwave-safe mug, combine 1 heaping teaspoon HERSHEY'S Cocoa, 2 heaping teaspoons sugar and dash salt. Add 2 teaspoons cold milk; stir until smooth. Fill cup with milk. Microwave at HIGH (100%) 1 to 1-1/2 minutes or until hot. Stir to blend; serve.