There are simply not enough words for "simple" and "perfect" to describe this do-ahead one-dish meal--the very best thing to bake and serve the crowd that is crowding hungrily around your kitchen looking for breakfast on, say, a holiday morning. Because you assemble it the night before, all you have to do the next day is pop it in the oven. When it emerges, the whole thing will be appealingly brown and bubbly and oozy, and the tortillas will have gotten thick and soft in a way that makes it kind of like quiche only, somehow, better. This recipe is also endlessly adaptable: you can simply omit the chiles, or swap in something else like sautéed mushrooms and onions.
Grease a 9- by 13-inch baking dish.
Cover the bottom of the dish with tortillas, overlapping as little as possible. You will use 2 tortillas per layer: Tearthem in half, and by the time you get all the flat sides pressed up against the edges of the baking dish, it's pretty much all set. Now sprinkle the tortillas with 1/2 of the chiles and 1/3 of the cheese, then add another layer of tortillas and top it with the rest of the chiles and another 1/3 of the cheese. Add the final layer of tortillas, sprinkle it with the remaining cheese, and then whisk together the eggs, milk, and salt in a bowl, and pour this over the whole casserole.
Cover and refrigerate overnight.
In the morning, heat the oven to 350 and get the casserole out of the fridge. Let come to room temperature. Bake for 35 minutes. When done it will be gloriously browned around the edges, and it will jiggle not at all.
Let it sit 5 or 10 minutes before cutting it, so that it has time to set up. If you cut into it, and it's very obviously not cooked through (e.g. raw egg), then pop it back into the oven for 10 more minutes. But what is normal is for there to be a little bit of clearish liquid that separates out as you slice it: this is from the chiles and is fine.