Bring the broth to a simmer in a large heavy pot. Add the dried chipotle pepper and black-eyed beans. Cover and simmer on low until the beans are tender, about 3 hours.
While the beans are cooking, heat the olive oil in a medium sauté pan over medium heat. Add the onion slices, carrots, red pepper, celery, and Serrano, and sauté for 20 minutes, or until the onion begins to lightly brown. Add the garlic and sauté for another 5 minutes.
Add the vegetables to the soup pot, and stir into the beans. Add the vinegar to the sauté pan and scrape up any cooked bits. Add to the soup pot.
Add the thyme, mustard and all of the spices except the salt. Simmer until beans are very tender. Add the salt.
Ladle the soup out into bowls, and top each bowl with one tablespoon scallions and one tablespoon cheddar cheese
Serve over rice with a side of cornbread.