Prepare the chicken: Pat the chicken thighs dry and lightly season both sides with salt.
Sear the chicken: Heat the oil in a large soup pot or Dutch oven over medium heat until it shimmers. Carefully add the chicken skin-side down. Sear for about 3 minutes per side, or until lightly golden. The chicken will not be cooked through at this point. We are only browning it and rendering some of the chicken fat to flavor the soup.
Add the aromatics: Keep 2 scallions whole and finely chop the remaining 2 for garnish. Lightly pound the pale parts of the whole scallions with the handle or flat side of a knife until slightly flattened, then fold them in half. Add the bruised scallions and ginger to the pot.
Simmer the soup: Pour in the chicken broth. Cover and bring it just to a boil over medium-high heat. Reduce the heat to medium-low and simmer, covered, for 20 minutes. The chicken should be cooked through and easy to pull from the bones.
Prepare the slurry and eggs: While the soup simmers, combine the starch, pepper, turmeric, and 2 tablespoons of water in a small bowl. Mix until smooth, adding the remaining tablespoon of water if needed to make a pourable slurry. In a measuring cup with a spout, gently whisk the eggs just until the yolks and whites come together. Avoid whisking vigorously or creating lots of bubbles.
Shred the chicken: Remove and discard the ginger and whole scallions. Transfer the chicken to a plate. Remove the skin and bones, then shred the meat into bite-size pieces.
Season and thicken the soup: Taste the broth and add light soy sauce or coconut aminos only if needed. Return the shredded chicken to the pot and bring the soup back to a simmer over medium heat. Stir the slurry again, then pour it into the soup while stirring. Cook for about 30 seconds, until the broth looks lightly glossy and slightly thickened but is still soupy.
Bring the soup to a low boil: Let the soup become hotter than a simmer, with small, steady bubbles rising across the surface. It should not churn vigorously like a rolling boil.
Pour in the eggs: Turn off the heat. Immediately pour the eggs from the spouted measuring cup in a thin, steady stream—not all at once. Move the spout around the pot to distribute the eggs evenly, and do not stir while pouring.
Let the eggs set: Leave the eggs undisturbed for a few seconds. Slowly move a pair of chopsticks through the soup once or twice to separate any very large pieces. The eggs should form soft, silky, flower-like ribbons rather than tiny, broken bits.
Serve: Finish with a drizzle of toasted sesame oil and the chopped scallions. Serve hot or warm.
Notes
Make ahead and freeze: For the best texture, prepare the chicken soup base without the slurry or eggs. Refrigerate or freeze the base, then reheat it until gently boiling. Add the slurry and form the egg ribbons shortly before serving. Freezing the finished soup can make the eggs lose their soft, silky texture.
Storage and reheating: Store the finished soup in an airtight container in the refrigerator for up to 4 days. Reheat it gently on the stovetop over medium-low heat until hot. Avoid a hard boil, which can make the eggs firmer.
Instant Pot instructions
Select Sauté and wait until the pot is hot. Season the chicken with salt and add 2 tablespoons of oil.
Place the chicken skin-side down and sear for about 3 minutes per side, or until lightly golden. Press Cancel.
Add the bruised whole scallions, ginger, and chicken broth.
Secure the lid and seal the pressure valve. Cook on High Pressure for 10 minutes. Allow the pressure to release naturally for 5 minutes, then carefully release the remaining pressure.
Remove the ginger, whole scallions, and chicken. Discard the aromatics. Remove the chicken skin and bones, then shred the meat and return it to the pot.
Select Sauté and follow the stovetop instructions for seasoning the broth, adding the slurry, and forming the egg ribbons.
Turn off the Instant Pot as soon as the soup reaches a gentle boil, then immediately stream in the eggs.