1 pound dried black beans
1 medium onion, finely chopped
1 green bell pepper, finely chopped
3 cloves garlic, minced
1 ham bone or smoked ham hock
1/2 cup olive oil
Salt and freshly-ground black pepper
1/3 cup white or cider vinegar
Chopped raw onion
Chopped red pepper
The night before cooking the soup, place beans in a colander and wash them with cold running water. Pick out any rocks or beans that are broken or shriveled. Put the beans in a large (4 quarts or larger) Dutch oven or soup pot with a lid and cover with enough cold water so that it comes to one inch over the top of the beans. Soak overnight.
The next day, drain the water out of the pot and refill with clean cold water. Add enough water so that it comes an inch above the beans. Stir in the chopped onion, pepper, and garlic. Add the ham bone or hock, and stir in the olive oil. Add 2 teaspoons salt and a generous quantity of black pepper.
Bring to a boil over high heat. Skim off any white foam, then reduce the heat to low and cover. Simmer for 4 to 5 hours, until the beans are very soft and the soup is creamy, not watery. Check after 2 hours. If the beans seem dry or stewy, add another cup of water. The final consistency should be velvety and thick, and the soup should coat the back of a spoon. (The beans will soften in the first two hours. The goal is to continue cooking the soup until some of the beans break down and create the smooth, thick soup base.)
When the soup is nearly finished, stir in the vinegar and simmer for an additional 15 minutes, uncovered. Pull the ham bone out of the pot — the meat that hasn't already fallen off should be easy to pick off; roughly chop and return the meat to the pot.
Serve over rice (optional) and garnish with chopped raw onions and sour cream. Also, if you like, little bits of chopped chicharrónes can be garnished on top. Add some sweet fried plantains as a side dish!
This makes a large pot of soup, but it freezes very well.