Mix sugar, cornstarch, cocoa, and salt in 2-quart saucepan. Stir in milk gradually. Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir 1 minute.

Stir at least half of the hot mixture gradually into the egg yolks. Blend this into the hot mixture in the saucepan. Boil and stir 1 minute.

Remove from heat; stir in vanilla. Pour into dessert dishes.

Cool slightly before refrigerating.