In a large soup pot, sauté onions, ham fat, & ham for a few minutes, then add garlic & cook 2-3 minutes. Mash tomatoes (to make smaller pieces) & add to pot. Add bay leaves & potatoes. Add water/broth to cover ingredients. Cover & simmer 2.5 hrs. If soup is too thin, mash some of the beans against the side of the pot. If too thick, add more water. Cook uncovered for 30 minutes longer. Add salt & pepper to taste.