Remove the husks and silks from the fresh corn (elotes) and rinse them thoroughly to remove any remaining silk. Stand each ear of corn upright on a cutting board and use a sharp knife to cut the kernels off the cob.
Scrape down the cob to extract as much of the milky substance as possible. Collect the kernels and the extracted milky liquid in a bowl.
Transfer the corn kernels and the extracted milky liquid to a blender. Add the milk to the blender as well. Blend until you achieve a smooth, creamy consistency.
Strain the blended mixture through a fine-mesh sieve or cheesecloth into a bowl to remove any remaining solids. This step ensures a smoother texture for your Atole de Elote.
In a large saucepan, add the water and the cinnamon stick (or ground cinnamon if using). Mix well. Place the saucepan over medium heat, cover it, and bring the mixture to a simmer. Allow it to simmer for about 10 minutes until the water turns a cinnamon color.
Pour the strained corn and milk mixture into the water-cinnamon mixture. Dissolve 1 tablespoon of cornstarch in a small amount of cold milk or water to create a slurry.
Add the cornstarch mixture to the atole and stir until combined. Bring the atole back to a boil, stirring constantly, then reduce heat to low and simmer for 2 minutes or until thickened.
Taste the Atole de Elote and adjust the sugar if needed. Remove the cinnamon stick if you used one. If you're using vanilla extract, add it at this stage for flavor. Pour the Atole de Elote into mugs or cups and serve it hot. You can garnish it with a sprinkle of ground cinnamon or a dusting of cocoa powder if desired.