Prepare the Chicken: Heat oven to 400 degrees F. Line a baking sheet with aluminum foil.Rub chicken on both sides with salt and ancho chili powder.Heat the oil in a large soup pot over medium heat. Add chicken thighs, skin-side-down and cook until the skin is golden brown, about 12 minutes. Transfer the chicken, skin-side-up, to the prepared baking sheet and roast until the chicken is cooked through; about 20 minutes. Once roasted, transfer to a plate and allow to rest for 10 minutes.Sometimes the chicken skin can be a bit stubborn when you are removing it from the pan. If some is left stuck to the bottom of the pan, don’t worry. Scrape up the larger pieces and place them on top of the chicken thighs. Leave the smaller bits in the pot, they will be used in the soup.When you are able, remove the skin from the chicken and shred the meat. Either discard the skin or save it as a topping for the soup.Prepare the Soup: While the chicken roasts in the oven you can make the soup.Remove all but 1 tablespoon of the chicken fat left in the pot from browning the chicken thighs then add the onions, celery, jalapeño, garlic, chili powder and cumin. Cook until the onions are soft, about 10 minutes.Stir in the bay leaf, corn, chopped tortillas and the chicken stock. Bring to a boil, lower the heat, season to taste with salt and pepper and simmer uncovered for 20 minutes.Add the tomatoes and simmer uncovered for 10 minutes. Stir in the shredded chicken and the lime juice.Just before serving the soup, turn the broiler to high then broil the chicken skin (if using) until crisp, about 1 minute. Cut into strips.Divide the soup between bowls and top with cilantro an extra squeeze of lime, avocado, cheese, crispy tortilla strips and the reserved crispy chicken skin.