Heat the coconut oil in a large pot and gently cook the onion with a pinch of salt until very soft.
Stir in the ginger and garlic and cook for 1 minute.
Add the chicken broth, water, salt and chicken thighs. Bring to a simmer, cover and cook for 20 minutes. Remove the chicken thighs and set aside to cool a little, then slice thinly.
Cook the noodles of your choice in a separate pot, or if using zoodles there is no need to cook them.
Add the sliced chicken back into the soup along with the spinach, lemon juice and chilli flakes. Cook for 1 minute and taste for salt, chilli and lemon.
Place noodles or zoodles in the bottom of each bowl, ladle over the steaming soup and sprinkle with shallots, coriander leaves and sesame seeds and top with a drizzle of toasted sesame oil.