Poach the chicken breast in simmering chicken broth until done through, about 10 minutes.
Set the poached chicken aside until it is cool enough to handle and shred.
Combine chicken broth, chicken, red onion, carrots, potato, tomato paste, bay leaf, garlic, chipotle and jalapeno chilies, oregano, cumin and salt and pepper in a large saucepan over high heat.
Bring to a boil, then reduce heat to low and simmer for 20 minutes.
Taste and correct seasoning, if necessary.
Add zucchini, squash, pepper, lime juice, and sherry.
Bring again to a boil, then reduce heat and simmer 15 minutes.
Add cilantro and mint. Stir, then remove from heat.
Fry tortilla strips in hot oil until crisp.
Drain the fried tortilla strips on paper towels and set aside.
Ladle the soup into each bowl.
Sprinkle with shredded cheese and tortilla strips.
Garnish each bowl with an avocado slice and cilantro sprig.