In a saucepan over medium heat, warm the milk until it just begins to simmer and then remove from heat.
In a medium bowl, whisk together the egg yolks, 3/4 cup of the sugar, and the salt until smooth.
Sift the flour and cocoa powder over the egg mixture and whisk until smooth.
Add the hot milk, 1/4 cup at a time, to the egg mixture, whisking constantly, then pour the mixture back into the pan.
Stir constantly over medium heat until the mixture thickens and comes to a boil, about 4 minutes.
Reduce the heat to low and stir constantly until the mixture coats the back of the spoon, about 1 minute longer.
Add both chocolates and stir until melted, then stir in 1 teaspoon of the vanilla.
Pour the filling into the crust and refrigerate, uncovered, until chilled, about 2 hours.
In the bowl of a stand mixer, combine the egg whites and the remaining 1 cup sugar.
Set the bowl over (but not touching) simmering water in a saucepan (you might want to wear oven mitts, or use kitchen towels to protect your hands from hot steam).
Whisk until the sugar is dissolved and the mixture is hot to the touch, about 2 minutes.
Place the bowl on the mixer fitted with the whisk attachment and add the remaining 1 teaspoon vanilla.
Beat on high speed until the meringue cools and stiff peaks form, about 4 to 5 minutes.
Mount the meringue on top of the pie and lightly brown with a kitchen torch (or brown under the broiler for 3 - 5 minutes...watch closely...don't let it burn!).