Chop onion and tomatillos; mince garlic. Set aside separately.
Heat oil in a large skillet over medium. Add onions and cook for 5 minutes, or until translucent.
Stir in tomatillos, garlic, and cumin. Cook for 2 minutes, then transfer to a large crockpot.
Drain and rinse beans; add to crockpot along with green chilies, broth, chicken, cilantro, oregano, chili powder, salt, and bay leaves.
Place lid on crockpot and cook on high for 4 hours, or on low for 8 hours.
Discard bay leaves. Remove chicken; shred with 2 forks and return to crockpot.
Serve chili topped with crumbled tortilla chips, sour cream, and chopped green onions.