1
Place beans in heavy large pot with enough cold water to cover by at least 3 inches. Let stand overnight.
2
Char chilies over gas flame or in broiler until blackened on all sides. Enclose in paper bag; let stand 10 minutes. Peel, seed, and chop chilies. Set aside.
3
Drain beans. Return to pot. Add enough cold water to pot to cover beans by 3 inches. Simmer until beans are almost tender, stirring occasionally, about 1 hour. Drain well.
4
Melt butter in clean heavy large pot over medium heat. Add onions and saute until tender, about 15 minutes. Add flour and stir 5 minutes (do not brown). Gradually whisk in chicken broth and half and half. Simmer gently until thickened, about 10 minutes. Add reserved white beans and roasted chilies, shredded chicken, and next 5 ingredients. Simmer gently to blend flavors, about 20 minutes. (Chili can be made 1 day ahead. Chill until cold, then cover and keep chilled. Rewarm before continuing.)
5
Add grated cheese and sour cream to chili; stir just until chili is heated through and cheese melts (do not boil). Ladle chili into bowls and garnish with cilantro and green salsa. Serve.
