Meanwhile, heat 3 tablespoons of olive oil in a large pot or Dutch oven. Add the onions, celery, and carrots and cook over medium-low heat for 10 minutes, or until the onions start to brown. Add the garlic and cook for 30 seconds. Add the chicken stock, tomatoes with their puree, jalapenos, cumin, coriander, 1 tablespoon salt (depending on the saltiness of the chicken stock), 1 teaspoon pepper, and the coriander, if using. Cut the tortillas in 1/2, then cut them crosswise into 1/2-inch strips and add to the soup. Bring the soup to a boil, then lower the heat and simmer for 25 minutes. Add the shredded chicken and season to taste. Serve the soup hot topped with sliced avocado, a dollop of sour cream, grated Cheddar cheese, and broken tortilla chips.