Preheat the oven to 300 deg F. Cut the tortillas into matchsticks. Place them in an even layer on a baking sheet and toast in the oven, about 15 minutes. Or, toast strips by sauteeing them in a dry skillet over medium heat, tossing frequently. Reserve about 1/2 cup of the strips for a garnish. Crush the remainder in a food processor or blender.

Heat the oil in a soup pot over medium heat. Add the onion and garlic and cook, stirring frequently, until they have a sweet aroma, 5-6 minutes. Add the tomato puree and continue to cook, 3 minutes. Add the cilantro, chili powder, and cumin and cook for another 2 minutes.

Add the broth, crushed tortillas, and bay leaf. Stir well, bring the soup to a simmer and cook for about 25-30 minutes. Strain the soup through a sieve.

Serve the soup in heated bowls, garnished with the shredded chicken, cheddar cheese, reserved tortilla strips, and diced avocado.