In a small bowl, lightly beat egg whites & set aside.
In a large bowl, combine cocoa & cornstarch. Whisk 3/4 cup soy milk into cocoa mixture until completely smooth.
In large saucepan, combine remaining milk, sugar, & salt. Mix well. Bring to boil over high heat, whisking constantly. Remove pan from heat.
Whisk cocoa mixture into hot milk mixture. Bring to a boil over medium-high heat; boil for 2 minutes, whisking constantly. Remove pan from heat.
Gradually whisk 1 cup of hot cocoa mixture into the egg whites. Pour mixture back into pan. Cook over medium-low heat 2 minutes, whisking constantly. Do not boil. Remove pan from heat.
Add vanilla; blend well. Pour pudding into serving dish(es). Cool to room temperature. Cover & chill for 1 hr.