"I loved this drink growing up. It is very delicious and great on a cold chilly day. My Mexican grandmother used to make this for us when I was a kid, and now I make it for my kids. Very delicious. Serve hot, alone or you can top with whipped cream and dust some cinnamon over it. Sugar can also be less or more, suited to taste."
Combine 2 cups water and cinnamon in a saucepan over medium-high heat. Bring to a boil; let boil for 7 minutes. Drop in chocolate tablet and stir until dissolved, 5 to 6 minutes. Reduce heat to medium and cook for 2 minutes more.
Combine cornstarch and cold water in a small container with a lid; shake until mixed well.
Stir evaporated milk and sugar into the chocolate mixture in the saucepan. Add cornstarch mixture and stir well. Increase heat to a simmer and cook until slightly thickened, about 3 minutes.