Cooked in this easiest possible way, beans have many possibilities: for eating as is, with toppings, as fillings, or in soups. To flavor them, Lupe Romero Vidal, a home cook in Hidalgo, Mexico, uses fresh avocado leaves--which have a delicately herbal taste but are unavailable in the United States. However, the pungent herb called epazote, carried by Latino markets and many grocery stores in the Southwest, makes a great flavoring too. Even without either, the recipe will still be good. You can certainly use olive oil instead of lard, but it's not as traditional (and the lard is delicious).