To serve, ladle the hot soup into bowls, and then let everyone pick and choose from among the suggested mix-ins and toppings: toasted corn tortilla strips, lime wedges, shredded Monterey Jack cheese, diced green peppers, sliced scallions, diced avocado, and cilantro sprigs. You can also use leftover or store-bought roasted chicken in this soup; use two quarts homemade or reduced-sodium canned chicken broth instead of the cooking liquid.