Combine the cocoa, sugar, salt, and cornstarch in a sauce pan and mix well.
Slowly add the almond milk, whisking constantly to prevent lumps.
Bring this mixture to a boil over medium heat while whisking constantly.
Lower the heat to a simmer a few minutes until pudding begins to thicken, whisk time to time.
Remove from the heat and whisk the butter and vanilla.
Pour into one large bowl or 8 small serving bowls. Let them cool completely and refrigerate until thoroughly chilled.