A simpler nor more delicious recipe may not exist. Your guests will love it, and you can garnish with fresh raspberries for a more sophisticated presentation.
Whisk unsweetened cocoa, sugar, cornstarch, salt and milk in a medium saucepan. Bring to a boil over medium-low heat, stirring consistently until it thickens. Remove from heat and add vanilla. Pour into bowl and cover with plastic wrap. Refrigerate for at least 3-4 hours. To make this into a pie, pour pudding into a pre-baked pie crust instead of the bowl and then refrigerate.
Pie crusts that complement this fully are: Graham Cracker, Walnut Crust or the Ginger Snap Crust. For a traditional chocolate pie, prebake one regular pie crust before adding the pudding mixture. Garnish top of pie with a few raspberries, shavings of dark chocolate, or a dollop of vegan whipping cream.