In a saucepan, combine the milk, evaporated milk, and vanilla and warm up over a low heat.
Combine the cocoa powder, sugar, cornstarch and cinnamon in another bowl. Whisk the cocoa mixture into the warm milk mixture. Whisk the mixture frequently to prevent it from scorching.
Remove the mixture from the heat just after it has come to a boil. The mixture should be suuuuuper rich and thick!
Cook's Note: For grown-up kids: A shot of brandy, kahlua, or peppermint schnapps is really yummy!