Place 7 cups of milk in a large saucepan on medium-low or medium until it's steaming but NOT boiling. Stir occasionally.
While the milk is cooking, place the other cup of milk in the blender with the sugar, cornstarch, cocoa, and pinch of salt.
Once the milk on the stove is steaming, add the cup of milk/cocoa from the blender slowly while stirring.
Continue cooking, stirring constantly to keep it from sticking or burning, until the mixture thickens and comes to a light thick bubbling boil (not an aggressive rolling boil).
Remove from heat and stir in the vanilla. You can serve hot with whipped cream, though I prefer it stone cold from the fridge all on its own.