Rub the chicken thighs with a little salt and 5-spice powder and set aside for 10 mins.
Add the broth to a pot along with the star anise, ginger, peppercorns, Shaoxing wine (if using) and white parts of the spring onion. Bring to a boil, reduce the flame and simmer, covered for 20 mins.
While the broth simmers, heat 2 tsp of groundnut oil in a frying pan and add the chicken thighs. Sear on medium flame for 2 minutes till lightly browned on both sides. The cover and cook for 7-10 minutes till done. Remove from the pan, cool a little and cut into thick slices.
Once the broth has simmered for 20 mins, remove the spices and onions with a slotted spoon and add salt and white pepper.
Now add the vegetables, turn off the flame and cover for 5-7 mins. Ladle into bowls, add the chicken slices and serve.