Film the bottom of a large (3-quart) sauce pan with the lard or oil and set over medium heat. Add the garlic and cook until fragrant, about 30 seconds, then add in the black beans. Using a potato masher, mash the beans into a coarse texture and cook for 5 to 7 minutes.
Meanwhile, make the avocado-tomatillo salsa.
Scoop the beans into warm corn tortillas and garnish with cheese, salsa and cilantro.