Heat a knob of ghee or coconut oil in a heavy bottomed pot. 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 a minute. Stir in the cumin, coriander and a generous pinch of salt and pepper. Toast for 30 seconds then add the vegetable broth, diced tomatoes and jalapeños. Cut 3 of the tortillas in half, then cut them crosswise into ½-inch strips and add to the soup. Bring the soup to a boil, then lower the heat and simmer for 20 minutes. Add the beans and cilantro and simmer for 5 more minutes, until beans are heated through.
Serve the soup topped with sliced avocado, sour cream, grated cheddar cheese and broken tortilla chips.
To toast the corn tortillas for topping: Preheat oven to 350F. Slice into small strips and dry toast for about 10 minutes or until crispy.