2 cups (16 fl. oz./500 ml.) low-sodium beef broth, heated to boiling
5 ancho chiles
Corn or canola oil for frying
3/4 cup (3 oz./90 g.) chopped white onion
4 cloves garlic, minced
1 can (28 oz./875 g.) whole tomatoes, with juice
2 tsp. chopped fresh oregano
1/2 tsp. each ground cumin and chipotle chile powder
12 corn tortillas, 8 inches (20 cm.) in diameter
3 cups (12 oz./375 g.) shredded Monterey Jack or mild Cheddar cheese
6 green onions, minced
3/4 lb. (375 g.) Cotija cheese, crumbled
1/3 cup (2 oz./60 g.) sliced olives (optional)
In a heatproof bowl, combine the hot broth and chiles and let stand until the chiles are soft, 8-10 minutes. Drain, reserving the broth. Seed the chiles and coarsely chop.
In a fry pan over medium-high heat, warm 2 tablespoons oil. Add the onion and cook until translucent, 2-3 minutes. Add the garlic and cook for 1 minute. Transfer the mixture to a blender, add the tomatoes and their juice, the chopped chiles, the oregano and the cumin and process until smooth. Return the mixture to the fry pan over medium heat and cook, stirring, until it thickens and bubbles, about 2 minutes. Stir in the chipotle chile and 1 cup (8 fl. oz./250 ml.) of the reserved broth and season with salt. Cook for 1-2 minutes, then taste and adjust the seasoning. Continue to cook, stirring occasionally, until thickened but still pourable, about 10 minutes. Remove from the heat and pour a thin layer of the sauce in the bottom of an 8-by-12-inch (20-by-30-cm.) baking dish.
Preheat the oven to 375 degrees F (190 degrees C). Pour a thin film of oil into a fry pan placed over medium heat. Add a tortilla and heat for a few seconds until softened. Using tongs, transfer the tortilla to the baking dish. Sprinkle about 2 tablespoons of the Jack and some green onions down the center, roll up, and place, seam side down, at one end of the dish. Repeat to fill all the remaining tortillas, then pour the remaining sauce over them, covering completely, and top with the remaining Jack. Bake until the cheese melts and the tortillas have absorbed the sauce, about 25 minutes. Remove from the oven, top with the Cotija and the olives, if desired. Serve at once. Serves 4-6.