Pour 4 cups of milk into the medium pot, add the cinnamon stick and warm over medium-high heat. Keep an eye on it, it can heat faster than you think and you don't want it to boil.

Place the pan over medium-high heat and spread out the sugar over the surface. Let it stand for a minute until you see it start to carmelize (See photo).

At this point begin to stir the sugar with the wooden spoon. First, you will see crystals form or small "rocks" of sugar. With the spoon, stir and watch as the little rocks dissolve and it becomes a very clear, amber-colored syrup.

As soon as the caramel syrup forms, it's ready. Please don't delay in taking it off the heat, because it can burn quickly. Take a cup of the warm milk and carefully pour the milk over the caramel.

You will see a lot of bubbling as the caramel solidifies upon contact with the milk. Don't worry, keep stirring and it will dissolve.

When the caramel is completely dissolved, pour it over the rest of the warmed milk.

Dissolve the cornstarch in the last cup of milk. This milk must be cold. This is important because if it's not cold it won't dissolve easily.

Add the cornstarch mixture to the milk and caramel blend without stopping stirring. Continue cooking the atole for 5 minutes. It's important that you don't stop stirring to keep the milk and the caramel from sticking to the bottom of the pot.

As time passes, you will notice that the atole takes on a smoother, only slightly thicker consistency.

After 5 minutes, turn off the heat and let rest for a few minutes.

Pour the atole through a sieve to remove any pieces of cinnamon stick. Serve and enjoy!

You will see that when it cools the caramel atole will thicken, this is normal and desirable.