Place chicken breasts and stock in to a stockpot or casserole. Bring to the boil and let simmer for about 20 minutes, or until chicken is cooked through. Remove the chicken from the stock and set aside.
Put the leeks and carrots into the pot and simmer them for 10 minutes, or until tender.
Shred the cooled chicken and return to the pot. Add the cabbage and egg noodles and cook another 5 minutes or until the noodles are soft. The soup should be thick like a stew. Serve hot and flavour to taste with Thai chilli sauce.