1In a large heavy pot, heat the oil over moderately high heat. Add half the tortilla strips and cook, stirring, until pale golden, about 1 minute.
3Remove with a spoon and drain.
5Reduce the heat to moderately low. Add the onion, garlic and spices and cook. Stir occasionally for 5 minutes.
7Add the broth, tomatoes, bay leaves, salt, cilantro leaves. Bring to a simmer. Cook uncovered for 30 minutes. Remove the bay leaves.
9In a blender puree the soup in batches. Pour it back into the pot. Add the chicken, bring the soup back to a simmer and simmer until just cooked through for about 1 minute.
11Stir in the avocado.
13To serve, put the remaining tortilla strips in bowls, top with the cheese, and pour in the soup.
15Sprinkle with the chopped cilantro, if using, and serve with the lime wedges if using.