Place chicken, sugar, fish sauce, ginger and spring onions in a large pot and cover with plenty of cold water.
Bring chicken to the boil, and reduce to a simmer, cooking for one hour. Skim off any scum that forms on the surface of the broth during the process. Remove the chicken and cook the stock for another 20 minutes.
Drain the stock through a fine sieve and discard the ginger and spring onions.
Remove the meat from the chicken and shred or cut into thin, bite sized pieces. You can refrigerate the chicken and the stock at this stage, and come back to it in a day or two if you like. If you do refrigerate the stock, peel off any fat that may settle on the top.
Arrange the basil, mint, sliced chilli, lime quarters and bean sprouts on a plate to share. Place Hoisin sauce in one large, or four smaller dishes.
Place the rice noodles and the chicken in a bowl and pour over boiling water to heat through. Drain off water and divide chicken meat, noodles and onion between four large soup bowls. Ladle over the stock and serve with the plate of condiments and Hoisin sauce.
Serve the bowls of soup and encourage guests to add the bean sprouts, mint, basil, chilli, lime juice and hoisin sauce to taste.