Heat the oil in a large, deep sauté pan (with lid handy) over medium heat. Add the corn tortilla and fry until golden brown, turning once to get both sides. Remove tortilla, and set aside—you’re using it to flavor the oil, then it's a snack or for the chickens.
Be careful here, as the oil is hot and you're adding liquid—I like to use the lid to shield the initial splattering. Get your bean masher in hand (a ladle, large wooden spoon, or an actual bean masher—see Rancho Gordo's website for an authentic Mexican masher) and add the beans and their cooking liquid all at once to the hot oil. Using your masher of choice, mash the beans while they simmer until they are the consistency you like, it takes me about 10 - 15 minutes. Adjust heat to keep the beans bubbling but prevent molten-lava splatters all over you and your stove. Cook longer to evaporate excess liquid, or add additional bean broth or water if they become too dry.