How to Make It
In a large, deep pot, cover the ribs with 10 cups of water and add the salt. Bring to a boil, then cover partially and simmer over low heat until the meat is tender, 1 1/2 hours.
Transfer the ribs to a large plate; keep warm. Skim off excess fat from the cooking liquid; you should have about 6 cups of liquid. Add the onions, garlic and serranos to the pot and bring to a boil. Simmer over moderately low heat for 20 minutes. Add the poblanos and tortilla pieces; let cool. Working in batches, coarsely puree the cooking liquid.
Return the liquid to the pot. Add the ribs and simmer over moderately low heat until the stew is slightly thickened, about 15 minutes. Stir in the chopped cilantro and serve with the cheese, radishes, lime wedges and cilantro sprigs.