- Heat the peanut oil in a large soup pot set over medium heat.
- Once hot, add the lemongrass and ginger, cook for 30 seconds or until fragrant.
- Slowly pour in the chicken broth, rice vinegar, soy sauce, brown sugar, Sambal Oelek, Chinese 5-spice and pepper.
- Cover and bring to a boil. Once boiling, add the chicken thighs and mushrooms. Reduce the heat to a simmer, cover and cook for 25-30 minute or until the chicken is cooked through, tender and falling off the bone.
- Remove the chicken from the soup and shred with two forks or your hands. Return the chicken to the soup and stir in the bok choy and limejuice. Continue cooking for another 10 minutes.
- Meanwhile, bring a large pot of water to a boil and boil the udon noodles according to package directions. Drain.
- Divide the noodles among your bowls and ladle the soup over the noodles. Top each bowl with fresh cilantro, shredded carrots, chiles, green onions and sesame seeds.
*If you prefer, you can make this soup in the morning and allow it to simmer over low heat all day. Do not add the bok choy and limejuice until ready to serve. If you cook the bok choy all day, it will loose its texture.