In a hot wok coated with oil saute onions until caramelized. Add galangal, chilies, lemon grass and leaves. Deglaze with fish sauce. Add chicken stock and slowly simmer to a 20 percent reduction. Strain and keep hot. Check for seasoning. In a very hot wok coated with oil stir fry mussels until they start to open. Add leeks and carrots. Season. Check again for flavor. Serve immediately.