Rinse beans, place in pot and soak overnight. Or use quick soak method - cover with water, bring to a boil, cover and let sit for one hour.
Drain beans. Cover with fresh water, add bay leaf and bring to a boil. Reduce heat and simmer for 45 minutes to an hour, or until beans are soft. (Watch as beans simmer and add more water if needed). Remove bay leaf and drain, reserving about a cup of the liquid.
Heat lard, fat or oil in large frying pan, and saute onions and garlic until translucent.
Add beans to pan, and mash with a potato masher them as you cook them, adding some of the reserved liquid if they are getting too dry. Season to taste with cumin, salt and pepper.