Quick Cuban Black Bean Soup

1 tablespoon olive oil
1 onion, chopped
1 celery rib, chopped
2 cloves garlic, chopped
2 teaspoons dry mustard
3 cans black beans, rinsed and drained -- 16 oz each
1 teaspoon honey
3 cups vegetable or chicken stock
2 tablespoons dry sherry (optional)
1/2 teaspoon hot pepper sauce
salt and pepper to taste
1 cup chopped tomato
1 cup chopped sweet onion
1 cup plain nonfat yogurt
1/2 cup chopped cilantro

In a large heavy saucepan, heat the oil over medium heat. Add the onion, celery, and garlic, an cook stirring occasionally until the vegetables begin to soften, about 5 minutes. Stir in the mustard and cook for 1 minute. Add the beans, honey and 3 cups of water to the pot. Bring to a boil, reduce the heat to medium low, and simmer uncovered until the vegetables are very tender and the liquid is somewhat reduced, about 20 minutes.

Puree the soup base in a food processor or blender, in batches if necessary, until smooth. Return the puree to the cooking pot, stir in the broth, and simmer over medium heat until heated through, about 5 minutes. The soup should be quite thick but not so thick as to mound on a spoon. Stir in sherry and season with pepper sauce, salt and pepper. Serve tomato, onion, yogurt and cilantro at the table as garnishes.