Wash the meat, peel and halve the onions. Bring both to the boil in 1.5 litres of cold water. Season with salt and peppercorns. Cover and simmer for about 1 1/2 hours at low heat.
In the meantime clean and wash the celery and cut it into wafer-thin pieces. Peel and wash the carrots. Nick the carrots lengthwise all around so that flowers appear. Rinse sprouts and drain well.
Carve the chillies lengthwise, remove seeds and chop finely. Peel ginger, also dice very finely. Prepare noodles in boiling salted water according to package instructions. Pour stock through a sieve, cut meat into strips.
Carefully heat sesame oil. Fry ginger and carrots in it, season with salt. Add celery, meat and chilli. Add the stock, simmer for 15 minutes. Wash the basil, cut the leaves into strips, one on top of the other.
Finally add the sprouts and basil to the soup and season with salt and soy sauce. Fill the noodles in portions. Add hot soup. Serve garnished with basil.