Make the tortillas strips; Brush both sides of the 6 tortillas with 2 tablespoons of olive oil. Stack the tortillas and cut into 1/4-inch strips. Place in single layer on cookie sheets. Bake 8 to 10 minutes until strips begin to brown. Sprinkle with salt and set aside to cool; strips will become crisp when cooled.
Make the tortilla soup; Heat 2 tablespoons olive oil in a heavy stockpot over medium heat. Add the onions and garlic and sauté for 5 minutes or until tender and translucent. Add the cumin, ancho chile powder, oregano, salt, pepper and tomato paste and sauté 1 minute longer.
Stir in the tomatoes with juice, the 2 chopped tortillas, and bring to a boil. Lower the heat and simmer, partially covered for 5 minutes. Remove from heat, add one cup of the stock and puree with a hand blender (or puree in a traditional blender) until smooth. Add the chicken and remaining 5 cups of stock. Bring the soup back up to a simmer and cook for another 15 minutes or until chicken is cooked through. Add lime juice and season to taste with salt and pepper, if needed.
Ladle the soup into bowls and garnish with desired toppings.
Notes
*You can find ancho chile powder at most Bulk Barns, Latin grocery stores, or if you live in the Kitchener-Waterloo area you can also find it here.To make this soup vegan or vegetarian, replace the chicken stock with vegetable stock or water, omit the chicken and replace with 1 can black beans, drained and rinsed.