Another great recipe from The Complete Vegan Kitchen Cookbook:
Wash the beans in a large collander and throw away any skins that float to the top. The night before soak the beans in a stock pot and pour over warm water that covers the beans for at least 4 inches. Let soak overnight. The next morning drain the beans and rinse the stock pot, then put the beans back in the stock pot and cover with 6 cups of cold water. Bring the beans to a boil over high heat and and then reduce the heat to medium and simmer the beans until soft, about 40 minutes. Skim away any foam that develops. The cooked beans should be covered by 2 to 4 inches of cooking liquid at all times.
In another large stock pot, heat the oil (I use water or vegetable broth) and add the onions and garlic and continue sauteing until a light golden brown. When the onions are nicely carmelized, add the beans and the cooking liquid. After they simmer then puree the soup with a hand blender. Adjust the thickness with water. Add salt and pepper to taste adn stir in the sage. This is where you can add the rest of the oil listed, but it is not recommended or needed.
Serving suggestions: Serve with your favorite wheat bread or you can serve this over rice.
I always omit the oil. It is not needed for sauteing or flavor. This is a great tasting soup and if you want to add a few more ingredients you can add corn or hatch green chilies. The spicey flavor of the chilies is very nice with this soup. I also add frozen kale to this soup. My trick is to strip off the leaves of kale when it is plentiful in the summer and freeze the leaves in plastic baggies. You then take the bags out of the freezer and crunch up the upper half and pour into your soup when it is simmering. The kale will look like parsely but the nutritional value of kale is tenfold.