The stock for this soup should be as clear as a teardrop. Only half the noodles are required, so keep the rest in an airtight container in the refrigerator for up to a week.
Put the chicken in a large pan, add the water and bring to the boil. Then simmer for 5 minutes. Skim the surface. Add the onion, carrot, parsnip, leek and salt to the pan, cover and simmer over a low-medium heat for 45 minutes, until the chicken is tender.
Using a slotted spoon, remove the vegetables from the pan and discard them. Transfer the chicken to a plat