In a Dutch oven over medium heat, add oil and when hot, add onion, jalapeno pepper, tomatoes, garlic, chipotle purée, oregano and cumin. Sauté the ingredients, stirring constantly, until very soft, about 8 to 10 minutes. If more oil is needed, add a little. Pour in 2 cups chicken broth and cook for 20 minutes.
Transfer the mixture into the jar of a blender. Cover but remove the cap so the steam can escape and cover with a clean dish towel; process on low speed until very smooth. Return the mixture to the Dutch oven, increase the heat to high and pour in the remaining 4 cups of chicken broth. Season with salt and pepper and bring to a boil. Add chicken halves, reduce heat to medium and simmer until done, about 20 minutes.
Meanwhile, prep the flour tortillas by cutting in half. Take the two halves and cut in half again. Take a section and cut it into strips of about ½-inch wide.
In a cast iron pan, add oil and bring the temperature to between 350ºF to 360ºF. Working in batches, add the strips in a single layer and flip them until golden brown, about 45 seconds. Transfer them to a plate lined with paper towels to remove any excess oil. Set aside while frying the remaining strips.
Back to the soup….
Remove the chicken and place in the bowl of a stand mixer with the paddle attachment on; process on medium speed until shredded, about 30 to 45 seconds. Return the shredded chicken back to the Dutch oven, pour in lime juice and stir well. Bring it back to a gentle simmer and let it simmer for 5 minutes.
To serve, ladle soup in bowls and garnish with ¼ cup Oaxaca cheese, a couple slices of avocado, a few strips of tortilla, a big dollop of crema and for the finishing touch, sprinkle on fresh chopped cilantro. Serves 4.