In a large pot, add water, chicken thighs, garlic, ginger, and scallion whites. Sprinkle in salt and pepper. Bring to a boil.

Once boiling, reduce heat to medium-low and simmer uncovered for about 15 minutes.

In a small bowl, whisk together rice vinegar, soy sauce, and sesame oil. Set aside.

Carefully remove chicken, shred it, and return it to the pot along with noodles and carrots.

Cook noodles and carrots according to package directions, usually about 3-4 minutes.

Give the pot a stir to combine everything. Taste and adjust seasonings if needed.

Ladle soup into bowls, garnish with scallion greens and drizzle with sauce. Add chili oil if desired.