Heat a cast iron comal or frying pan and lightly toast the chiles, turning them from time to time so that they do not burn.While they are still pliable, slit them open and remove the seeds and veins. Cover them with hot water and let them soak for about 15 to 20 minutes.The SauceIn a small frying pan melt 2 tablespoons of lard or vegetable shortening and fry the almonds until they are well browned, stirring them so that they do not burn. Crush the almonds slightly and transfer to a blender jar.Skin the plantain, slice it think lengthwise, and fry it until golden on both sides. Transfer to the blender jar.Add the tomatoes to the ingredients in the blender and blend to a smooth puree--add a little water if necessary. Set aside.Separately, blend the chiles with the water, spices, oregano, and garlic to a smooth puree.In a medium to large frying pan melt 3 tablespoons of lard and cook the chile puree over a high flame for about 5 minutes. Remove from the flame and add the plantain-tomato mixture and continue cooking the sauce for about 5 minutes over a medium flame, stirring all the time so that it does not stick. Keep a lid handy as it will splatter about fiercely. Stir the broth gradually into the sauce and continue cooking it for a minute or so, then push the sauce though a food mill using the medium disk (or use a coarse sieve). Return the sauce to pan, add the salt and continue cooking for about 15 minutes over a low flame.The Enchiladas Heat 6 tablespoons of lard in a frying pan. Dip the tortillas one by one face down in the the oil for a few seconds then remove it and cover the face with a think layer of the sauce. Put some of the shredded meat across the tortilla, roll it up; place the tortillas side by side on the serving dish.Thin down the remainder of the sauce a little with the broth and pour it over the enchiladas. Garnish with the grated cheese and onion rings and serve immediately.Note: Once the enchiladas are assembled they should be used right away. The sauce can be made ahead of time and it freezes very well too.
From The Art of Mexican Cooking, by Diana Kennedy, 1972. This classic book is out of print but vintage copies are available. It is considered one of the best Mexican Cookbooks ever written.