The word birria means something deformed or grotesque, and it is used colloquially in the northwest to mean a mess or failure. This certainly looks a mess when it is cooked, but it is a very savory one. It is a really rustic dish. Usually a whole goat or lamb, although in some places just the offal, is seasoned with a paste of ground spices and chilies and cooked in a pit barbecue. One day ahead: There will be approximately 6 to 7 pounds of meat. Slash the meats in several places down to the bone and rub the salt well into it. Meanwhile, prepare the chili paste. Heat the comal (or griddle) and toast the chilies lightly, turning them from time to time so that they will not burn. Remove the veins and seeds. Put the chilies to soak in hot water for abt. 20 minutes, then transfer with a slotted spoon to the blender jar, add the rest of the ingredients, and blend to a smooth sauce. Cover the meat thickly with the paste and set it aside to season for about 18 hours. On serving day: Preheat the oven to 350F. Put the water in the bottom of a large Dutch over or casserole with a tightly fitting lid and place the meat on a rack so the it is just about the water. Seal the lid with a paste of flour and water and cook for about 3 1/2 to 4 hours, by which time the meat should be almot falling off the bones. Strain off the juices from the bottom of the pan, cool, and skim off the fat. There should be about 2 cups of juices left-if not, make it up with up to 2 cups of water. Blend the tomatoes to a smooth sauce. Put the sauce and the skimmed juices from the meat into a saucepan and bring to a boil. Serve each portion of mixed meats in a deep bowl. pour 1/2 cup of sauce over the meat and sprinkle with the chopped onion and oregano. Eat with tortillas. Makes 8 to 10 servings. From the Cuisines of Mexico by Diana Kennedy