Soak beans for 4-8 hours, or overnight. Drain and rinse.
In a large heavy skillet over medium heat, sauté onions and garlic in the olive oil over medium high heat. Cook until the onions are translucent and just beginning to turn brown.
Combine sautéed onions and garlic, soaked beans, and all of the remaining ingredients except the chicken in slow cooker. Cover and cook on low for 10-12 hours (or high for 4-5 hours), or until the beans are very tender. (Add additional broth or water if necessary.)
When beans are very tender, use an immersion blender or potato mashed to mash some of the beans up. This will slightly thicken chili. (Don’t overdo it though or you will have bean puree!)
Add chicken about thirty minutes before the chili is done.
Serve with toppings on the side: avocado slices, sour cream, lime wedges, tortilla strips, and chopped cilantro are all good choices.