Clean the chicken thoroughly and cut it into quarters.
In a large pot, add the water, chicken, onion, ginger, garlic, and star anise. Bring to a boil over medium-high heat.
Once boiling, reduce the heat to low and simmer for about 1 hour, skimming off any foam that forms on the surface.
After 1 hour, remove the chicken from the pot. Let it cool slightly, then shred the meat, discarding the skin and bones.
Strain the broth to remove the solids, returning the clear broth to the pot.
Season the broth with fish sauce, salt, and pepper to taste.