(Ethnic Vegetarian Kitchen)
Soak the beans in 4 quarts of water overnight. Bring the beans to a boil in a pot with their soaking water on high heat. (To help cut down on bean-related gassiness you can use fresh water, but add only 3 quarts or so.) Add the salt and bay leaves. Boil the beans, uncovered, for 1 hour, stirring occasionally. (To further reduced bean-related flatulence, add a 2-inch piece of kombu seaweed to the boiling water. This reputedly works for any beans you're cooking from scratch.) Reduce heat to a moderate level, cover the pot and cook the beans for 30 more minutes or until they are soft.
While the beans are cooking, heat the oil in a small pan. Sauté the onion, bell pepper, and garlic for about 5 minutes. When the vegetables are ready, add them to the simmering soup.
When the beans have softened, take a few spoonfuls of them out and mash them, then stir them back in. Repeat until you've mashed about 2 cups worth of beans. This will make the soup nice and thick. Adjust seasonings to taste at this point. If you wish, add the tablespoon of red wine vinegar. This is a hearty, good soup - but on the bland side. Gene suggests adding more cumin. I say a splash of your favorite liquid hot sauce never hurts.