Okay, here's my 2 cent's worth, and I know of what I speak (I am Mexican, I'm also an experienced and award winning Chef, specializing in the classic Mexican food of old)- the skinny is with chilaquiles it doesn't matter where in Mexico you're from. We all love them and they come in every color and flavor, they're all great.
As with other ethnic foods, people "bastardize" the recipes yet this doesn't mean they're still Mexican; it just means you've changed it to suit your tastes (we still don't like it, but whatever, c'est la vie....)
BUT to asnwer the question about what is chilaquiles, it's: day old tortillas are used because of the humidity issues (they fry better and they're no longer any good for tacos or guisados)- and once they're fried they don't get dumped in the sauce. The tortillas are placed on the place and then beans (if being used), chicken (we eat the whole chicken not just the breasts, people), the sauce, shredded cheese (if you like), sliced onion, crema, crumbled Cotija cheese, radishes (if you like), cilantro leaves (and sometimes salsa picante for those that like or just make a hot sauce to begin with..)
As far as sauces for these, the traditional is the red and green. The red is usually made with Guajillo chiles, but Anchos might be too sweet for me although they're good; the green with tomatillos of course. I've also made them with Mole (great!), Peanut Sauce, Salsa Ranchera, etc. so use any sauce you have available. The toppings are open, the one's I listed are the "traditional" ones and NO lime. If you put the tortillas into the sauce, they'd start getting soft and the point is they be crisp, so the sauce on top only. Yes, you can use shredded beef, pork, (I've used carnitas), vegetarian, rajas Poblanas, turkey, but chicken is still the most prevalent.
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