How to Make It
Set a lightly oiled large cast-iron skillet over moderately high heat. Add half of the chiles and cook, pressing occasionally, until lightly toasted, about 2 minutes per side. Transfer to a plate. Repeat with the remaining chiles. Let cool slightly, then remove the stems and seeds and rinse the chiles.
In a large bowl, combine the chiles with the 2 cups of boiling water and let soak until softened, about 20 minutes; use a plate to keep the chiles submerged.
Meanwhile, lightly oil the cast-iron skillet again. Add the garlic and onion wedges and cook over low heat until lightly charred, about 20 minutes. Transfer to a food processor. Add the chiles with their soaking liquid and puree. Strain through a coarse sieve, pressing hard on the solids with a rubber spatula.
In a large pot, cover the chicken breasts with the remaining 6 cups of water and simmer over low heat until just cooked through, about 15 minutes. Transfer the chicken to a large plate and let cool, then slice crosswise 1/4 inch thick; reserve 3 cups of the poaching liquid.
In a large skillet, heat 1 tablespoon of the oil. Add the chile puree and 1 cup of the cilantro and cook over moderate heat for about 10 minutes, stirring frequently. Scrape the sauce into a large bowl and add the cloves and cinnamon. Season with 2 1/2 teaspoons of salt and 1/2 teaspoon of pepper and stir in the reserved poaching liquid.
In a medium skillet, heat 1/4 cup of the oil over moderate heat. Fry 1 tortilla at a time until it starts to puff up but is still pliable, about 30 seconds per side. Transfer the fried tortillas to a large baking sheet; add more oil to the skillet as needed.
Preheat the oven to 350°. In a 15-by-12-inch shallow baking dish, spread 1 cup of the chile sauce. Cover with 8 slightly overlapping tortillas, half of the chicken and 1/4 cup of the cilantro. Season with salt and pepper. Cover with 2 cups of the sauce and sprinkle with 3/4 cup of each cheese. Continue layering with 8 more tortillas and the remaining chicken and cilantro; press lightly. Season with salt and pepper. Add 2 more cups of sauce and sprinkle with another 3/4 cup of each cheese. Finally, press the remaining tortillas onto the pie and top with the remaining sauce and cheese.
Cover the pan tightly with foil, making sure the foil does not touch the cheese. Bake in the center of the oven for about 1 hour and 20 minutes, or until hot and bubbling. Serve hot with the sour cream.