For dried chiles, toast them on an ungreased griddle or heavy skillet over medium heat, turning regularly and pressing flat with a spatula, until very aromatic, about 30 seconds. In a small bowl, cover the chiles with hot water and re-hydrate 30 minutes, stirring frequently to ensure even soaking. Drain and discard the water. (Canned chiles need only be removed from their sauce.)
Roast the unpeeled garlic on the griddle or skillet, turning occasionally, until soft, about 15 minutes; cool and peel. Roast 1 1/2 pounds of the tomatoes on a baking sheet 4 inches below a very hot broiler until blackened on 1 side, about 6 minutes, then flip and roast the other side. Cool, then peel, collecting all the juices with the tomatoes.
In a food processor or blender, process the roasted tomatoes, rehydrated or canned chiles, and garlic to a medium-fine puree. Heat 1 tablespoon of the oil in medium-size (4-quart) pot (such as a Dutch oven or Mexican cazuela) over medium-high. Add the puree and stir for about 5 minutes as it sears and thickens. Set aside.
If using chorizo, cook in a little oil over medium heat, breaking up large lumps as you go, until thoroughly cooked, about 10 minutes. Scoop it out with a slotted spoon, draining as much oil as possible back into the skillet.
Pour 6 tablespoons of the remaining oil into the skillet and return to the heat. When quite hot (drop a stray noodle in – it should sizzle but not brown immediately), lay in about 1/3 of the noodle nests to fry until noticeably browned, about 1 minute, then flip and brown the other side. Remove with a slotted spoon, draining as much oil as possible back into the skillet, and drain on paper towels. Continue until all have been browned.
Add the broth, oregano, and pepper to the tomato sauce. Core the remaining 1 pound of tomatoes and chop into 1/4-inch bits. Add and simmer briskly until the sauce thickens to the consistency of a juicy tomato sauce, about 5 minutes. Taste and season with salt.
Add the noodles. In about 2 minutes pull the "nests" apart (they'll have softened enough to do it at this point), then add the zucchini and the chorizo (if you're using it). Simmer, stirring occasionally, until the noodles are tender but still firm, about 2 minutes.
If using the cream, add it now, raise the heat to medium-high and boil quickly until the sauce returns to its previous consistency. Taste again and readjust the salt, if necessary.
Stir in half of the grated cheese, scoop into a warm serving dish, sprinkle on the remaining cheese and the cilantro garnish, and it's ready to serve.
Recipe courtesy of Rick Bayless, Rick Bayless's Mexican Kitchen, Scribner, 1996