Combine chicken breasts, onion, garlic, tomatoes, north, salt, pepper, and green chili in your crockpot. Cook on high for 6 hours, then low until ready to serve. In each bowl, place a layer of cheese (whichever kind you like best--I love both of them!), then spoon the soup on top. Sprinkle with tortilla strips, cilantro, and avocado.