How to Make It
In a large heavy pot, heat the oil over medium high heat until hot. Sprinkle the ribs with 1 teaspoon salt and 1/2 teaspoon pepper, then brown the ribs, turning occasionally, until golden, about 6 minutes total.
While the ribs brown, pulse the pepper, onion, garlic and cilantro in a food processor until finely chopped to make a sofrito. Add the sofrito to the pot, scrapping up any browned bits. Stir in the water, bay leaves, cumin seed, and 1 teaspoon salt, then bring to a simmer. Simmer the soup, partially covered, 2 hours.
Peel the potato and the mango, then cut both into 1/2-inch pieces, discarding the mango pit, and stir into the soup. Continue to simmer the soup until the meat is very tender and the potatoes are falling apart, about 1 hour more.
Halve, pit, and peel the avocado then season the soup with salt and pepper to taste, discard the bay leaves, and divide the soup between serving bowls. Dice the avocado and divide between the bowls. Serve.