Cover chicken with water. Add 1 quartered onion, ½ teaspoon of the cumin, and 1 of the garlic cloves. Simmer until tender. Cool in stock; reserve ¼ cup stock. Remove bones from chicken and tear into large bite-size pieces. Set aside. In butter, sauté 1 chopped onion, 1 chopped garlic clove, green pepper, poblano pepper, and jalapeño. Add tomatoes, chili powder, remaining ¼ teaspoon cumin, green chilies, stock, Velveeta cheese, and chicken. Simmer, stirring constantly. When heated through, turn off heat and stir in sour cream. Serve over tortilla strips or tortilla chips.