Champurrado is another Mexican drink made with cacao beans that is really amazing. The difference from the Mexican hot chocolate is that ground corn is used to thicken it up (the same corn flour used to make tortillas) and it is not as sweet as the hot chocolate. If you have Mexican chocolate discs you can easily make champurrado by adding some corn flour until you have slightly thick chocolate.
However, last time we were in Mexico I picked up a bag of champurrado mix by a brand Kekua. The ingredients are: corn, sugar, cacao, cinnamon and soy lecithin. You add 3 tbsp of this mix to a cup of milk or water, boil it, froth it, done.
I really like this mix, it is perfectly sweet and thick, they just could have added a bit more of the cinnamon.