Peel off the tough outer layers of the lemongrass, leaving the tender white center, cut into 3-inch pieces and crush with the flat of a knife.
Pour stock in a saucepan, add in the lemongrass, galangal, lime leaves and ½ of the shallots. Bring to a boil keep an eye on it or it'll boil over, then reduce the heat, cover and simmer gently for an hour. Strain the mixture and discard solids. Return the stock to the pan.
Cut chicken into bite-sized chunks and set aside, add the chicken wings to the stock, add in the fish sauce, lime juice, chillies, sugar, coconut milk and the remaining shallots. Bring to a boil then reduce heat and simmer for 10 minutes then add in the chicken chunks and cook for another 5 minutes. Stir in chili sauce in the last few seconds and give it a good stir. If using only chicken pieces, boil for 8 minutes.
Meanwhile, boil dried noodles for 3 minutes, drain and rinse then divide into 2 bowls, pour in the coconut-chicken soup, garnish with some cilantro leaves and serve hot.
