Combine the fish sauce, ginger, garlic, chili and 1 tblsp sugar in a bowl, mix the chicken with this and leave to marinade at least one hour.
Heat some oil in a wok. Drain the chicken from the marinade and fry the chicken for a few minutes until cooked, remove from the pan, pour in the remaining marinade and the chicken stock with the rest of the sugar, let this bubble and reduce to a syrupy sauce, add the onion and return the chicken to the pan, cook for 5 more minutes.
Arrange on plates and top with a generous amount of the herbs.
You can roast the chicken skin in the oven while the rest of the dish is cooking, shred this and top the salad with it.