In a large bowl, add dried chiles and hot water. (If you're very sensitive to spicy food, you can also remove the seeds from the dried chiles, if desired.) Cover bowl with a large plate or plastic wrap and let the chiles soak on the counter for 20 minutes.
Using a slotted spoon, transfer the softened chiles into a large blender.
Add in 1 cup of the chile-soaked water, 1/2 cup of fresh water, garlic, salt and Mexican chocolate. Puree until completely smooth. Add more water if the sauce is too thick for your liking.