Melt the butter in a large pot over medium-high heat. Add the onions and sauté until translucent and beginning to brown around the edges, about 4 minutes.
Add the garlic and stir constantly until fragrant, about 30-60 seconds.
Increase the heat to high and stir in the broth, beans, chicken, green chiles, corn, cumin, and oregano.
Once the mixture comes to a low boil, reduce the heat and simmer for 15 minutes.
Stir in the cheese and sour cream until they melt into the soup.
Store: Keep leftovers in an airtight container in the refrigerator for 6-7 days.Freeze: Once cooled, freeze in a freezer-safe container or ziploc bag for 6 months.Thaw: Thaw the chili overnight in the refrigerator.Reheat: Reheat in a saucepan over medium heat until heated, about 6 minutes.