Heat the oil in heavy large pot over medium heat. Add the onion and cook until soft and beginning to brown, 6-7 minutes. Add garlic, chili powder, and coriander and stir. Cook together for 1 minute. Stir in the tomatoes with their juices, beans, chipotle pepper, and oregano. Add 5 cups of water and bring to a boil. Reduce heat to low, cover with lid slightly ajar and simmer until beans are flavorful and tender, anywhere from 2 - 4 hours (depending on the age of your beans). After 1 1/2 hours of cooking, add the sweet potatoes, quinoa, and salt. Place the pot's lid back on slightly ajar and allow to simmer on low heat until the beans are soft and the sweet potatoes and quinoa are cooked through. Add more water if the chili becomes too thick. Season to taste with salt and pepper. Serve with sour cream, cilantro, and green onion. Can make two days ahead. Store in refrigerator. Freeze leftovers.