Ingredients

9 to 12 (about 3/4 ounce total) stemmed, dried chipotle chilies (or canned chipotle chilies en adobo)
12 garlic cloves, unpeeled
4 1/2 pounds (9 medium-large round or 28 to 34 plum) ripe tomatoes
2 tablespoons plus 1/2 cup vegetable oil
Salt, about 1 3/4 teaspoons
4 cups (about 6 ounces) loosely packed, stemmed lamb's quarters (quelites) or 6 cups loosely packed spinach or 1/2-inch-long sliced chard leaves (you'll need a 12-ounce bunch)
2 medium (12 ounces total) zucchini, cut into 1/4-inch dice
2 medium ears corn, husked, kernels cut from the cob or 1 1/2 cups frozen corn kernels, thawed
1 pound (about 4 cups) shredded Mexican Chihuahua cheese or other melting cheese such as brick or Monterey Jack
16 corn tortillas, preferably slightly stale factory-made ones
About 1/3 cup chopped fresh cilantro, for garnish

For the Essential Quick-Cooked Tomato-Chipotle Sauce: Toast dried chilies on an ungreased griddle or skillet over medium heat, turning regularly and pressing flat with a spatula, until very aromatic, about 30 seconds.
In a small bowl, cover the chilies with hot water and let rehydrate 30 minutes, stirring frequently to ensure even soaking. Drain and discard the water.
If using canned chilies, simply remove the canned chilies from their canning sauce.
While the chilies are soaking, roast the unpeeled garlic on the griddle or skillet, turning occasionally, until soft (they will blacken in spots), about 15 minutes; cool and peel.
Roast the tomatoes on a baking sheet 4 inches below a very hot broiler until blackened on one side, about 6 minutes, then turn and roast the other side. Cool, then peel, collecting all the juices with the tomatoes.
Working in batches, in a food processor or blender, process the tomatoes with their juices, rehydrated or canned chilies and garlic to a medium-fine puree.
Heat 2 tablespoons of the oil in a medium-size (4-quart) heavy pot (such as a Dutch oven or a Mexican cazuela) over medium-high heat. Add the tomato puree and stir nearly constantly for 8 to 10 minutes as it sears and thickens. Taste and season with salt, usually about 1 1/2 teaspoons.

For the vegetables: In a vegetable steamer, steam the lamb's quarters (or other greens), covered, until tender, 3 to 5 minutes for the lamb's quarters, 2 to 3 minutes for the spinach or chard. Immediately spread out on a baking sheet to cool, then roughly chop.
Steam the diced zucchini until just tender, 2 to 3 minutes, then spread out to cool. Sprinkle the vegetables with 1/4 teaspoon of the salt. Set out the corn, tomato sauce and shredded cheese.

For the tortilla: Pour the remaining 1/2 cup oil into a small skillet and set over medium heat. Line a baking sheet with several layers of paper towels. When the oil is hot, quick-fry the tortillas one at a time for a few seconds per side, just to soften them. Drain the tortillas in a single layer on the paper towels, blotting them dry. Cut them in half.

Making the casserole: Turn on the oven to 350 degrees F. Lightly grease a 13- by 9-inch baking dish. Spread a thin layer of the sauce over the bottom, then lay out 8 tortilla halves in a single layer, arranging them to cover as much sauce as possible. Evenly spread on the greens, a scant 11/2 cups of the remaining sauce and 1 cup of the cheese. Top with another layer of 8 tortilla halves. Spread on the corn and the same amount of sauce and cheese. Top with a third layer of 8 tortillas, the zucchini and another round of sauce (scant 11/2 cups) and cheese (1 cup). Top with the remaining tortilla halves, sauce and cheese.
Cover lightly with foil and bake for 25 minutes. Uncover and bake for an additional 10 to 15 minutes, until bubbling and lightly browned. Let stand a few minutes before cutting into squares. Sprinkle with the chopped cilantro, then use a spatula (a squared-off metal one works best) to transfer the pieces to warm serving plates. Serves 8 as a main dish, 12 to 16 as an accompaniment.

Directions

Shortcuts: The sauce can be prepared with three 28-ounce cans of good-quality plum tomatoes without losing much quality (only a little roasty flavor). About 11/2 (10-ounce) packages of frozen chopped spinach (defrosted and well-drained) could replace the greens. From "Rick Bayless's Mexican Kitchen: Capturing the Vibrant Flavors of a World-Class Cuisine," with Deann Groen Bayless and Chicago food writer JeanMarie Brownson (Scribner)