Rinse pinto beans. Place beans in large cooking pot and cover with water. Let stand overnight.
Drain contents of pot and refill with water. Add quarter section of onion and whole garlic clove. Bring pot to a boil. Reduce heat, cover and cook until beans are tender, about one hour. Drain and return to stove.
Meanwhile, add oil to large skillet over medium heat. Add remaining garlic. Cook for about 1 minute. Add remaining onions and peppers. Sauté until onions are tender, about 3 to 4 minutes. Add chorizo and cumin. Simmer for about 20 minutes.
Add black beans, corn and crushed tomatoes to cooked pintos. Bring to a low boil and reduce heat. Add sautéed ingredients, stock and remaining spices. Stir. Cover and simmer until chili is ready to serve.