Asian Chicken Noodle Soup

Ingredients

1. 1 tablespoon cooking oil
2. 1 tablespoon Asian sesame oil
3. 1 onion, chopped
4. 2 ribs celery, cut into 1/4-inch slices
5. 4 cloves garlic, smashed
6. 1 1-inch piece fresh ginger, cut into thin slices
7. 2 tablespoons chili powder
8. 1/8 teaspoon dried red-pepper flakes
9. 1 1/2 quarts canned low-sodium chicken broth or homemade stock
10. 1 cup canned crushed tomatoes in thick puree
11. 1 1/2 pounds boneless, skinless chicken thighs
12. 3 tablespoons Asian fish sauce (nam pla or nuoc mam); see Note
13. 1 cup cilantro leaves plus 1/4 cup chopped cilantro (optional)
14. 1 3/4 teaspoons salt
15. 1/2 pound spaghettini
16. 1/2 head bok choy (about 1 pound), cut crosswise into 1/4-inch slices
17. 1/4 cup lime juice (from about 2 limes)

1. In a large heavy pot, heat both oils over moderate heat. Add the onion, celery, garlic, ginger, chili powder, and red-pepper flakes. Cook, stirring occasionally, for 5 minutes.
2. Add the broth, tomatoes, chicken, fish sauce, cilantro leaves, if using, and the salt and bring to a simmer. Reduce the heat and simmer, covered, until the chicken is just done, about 15 minutes. Remove the chicken; when it is cool enough to handle, cut it into bite-size pieces. Continue cooking the soup for 15 minutes longer.
3. Meanwhile, in a large pot of boiling, salted water, cook the spaghettini until just done, about 9 minutes. Drain and add the pasta and the chicken to the soup.
4. Add the bok choy; bring back to a simmer. Cook until just done, about 1 minute. Stir in the lime juice and chopped cilantro, if using.