"This is delicious as an "adult" version; however, the written instructions are wrong and would give you a big starch ball as she calls it:
Combine the cocoa powder, sugar and cinnamon in another bowl. Whisk the cocoa mixture into the warm milk mixture. Whisk the mixture frequently to prevent it from scorching.
She did NOT put cornstarch in with cocoa. Let mixture come to boil and reduce to simmer.
Pour a little of the cocoa mixture into the cornstarch to blend as a slurry, then add to the pot of cocoa. If cornstarch is added directly to cocoa, it would be a big starch ball. Wish your typists would pay better attention to the presentation and proof read before publishing!