For the Sauce:
Start by placing your dried chiles, yellow onion, and garlic cloves in a large bowl, and covering them with boiling water. Let sit for 15-18 minutes until the peppers are fully rehydrated.
After the peppers have rehydrated place in a blender, then add yellow onion, garlic cloves, chicken stock, vegetable oil, chipotle peppers, adobo, brown sugar and cinnamon. Blend until smooth, then strain into a small saucepan. Bring your sauce to a simmer, then reduce the flame to low and let cook 15 minutes. Taste your sauce for salt, and adjust. If your sauce sits out and starts to separate, just give it a whisk.
To Assemble
Heat 1/4 cup of vegetable oil in a large skillet on medium-low heat. lightly dip your tortillas in the sauce, then place in the skillet and fry for about 2 minutes on each side. Add some of the shredded chicken, then roll your enchiladas and plate. Pour a little bit of the sauce over your rolled enchiladas, and top with crema Mexicana, chopped onion, chopped cilantro and queso cotija.