How to Make It
In a saucepan, cover the beans with 2 inches of water and simmer over low heat, stirring occasionally, until tender, about 3 hours. Add water as necessary to keep the beans covered by 2 inches. Season the beans with salt and let stand for 5 minutes; drain, reserving 1 cup of the cooking liquid.
In a large skillet, heat the lard. Add the onion and cook over moderately low heat, stirring, until softened, 7 minutes. Add the beans, oregano and 1/2 cup of the reserved cooking liquid. Using a potato masher, coarsely mash the beans. Add more of the reserved bean liquid until the mixture is thick but not soupy. Season with salt. Transfer the beans to a bowl and serve with the tortillas, queso fresco and Spicy Pickled Nopales.