Mexican Chicken and Bean Soup

In a stockpot over moderately low heat, combine 2 teaspoons of oil and the onion, garlic, and jalapenos. Cook stirring occasionally, until the vegetables are soft. Add the chili powder, and cook and stir for 15 seconds. Add the tomatoes, beans, broth, chicken, and cilantro, and simmer for 10 minutes. While the soup simmers, cut the tortillas in half, stack them, and then cut them crosswise into 1/4-inch-wide strips. In a skillet, heat the 1/4 cup of oil over moderate heat; fry the tortilla strips in batches, stirring constantly for 15 seconds, or until crisp and pale golden. Drain the strips on paper towels. Divide the cheese among 4 soup bowls and ladle the soup over the cheese. Top with tortilla strips and dollops of sour cream. Garnish with avocado, if desired.