Place a large dry pot over medium heat, and add the quartered onion halves and ginger pieces.
Cook for about 4 minutes or until the onion’s edges brown a bit. This helps to release flavor. If the onions stick a little to the bottom of the pot, give them another stir.
Add the broth, coriander, fish sauce, hoisin sauce, oyster sauce, soy sauce, chili crunch, *cinnamon stick, sea salt, and black pepper to the pot.
Bring soup to a slow boil, then reduce heat and simmer for 30-45 minutes. (*REMOVE Cinnamon stick after 15 min).
While the soup is simmering, cook the noodles according to the package instructions. Once soft, drain, rinse, and set aside.
Assemble the garnishes for serving in individual small bowls.
About 5 minutes before the soup is finished simmering, use a slotted spoon to remove the onions and ginger pieces from the broth and discard them.
Increase the heat to a slow boil, add the thinly sliced chicken into the broth and cook for 2-3 minutes until firm
Divide the noodles among bowls and ladle chicken and broth on top.
Add desired toppings and enjoy immediately.