1 kg (2 lb) raw shrimps

1 tablespoon oil

8 cups hot water

1 1/2 teaspoons salt

2 stalks lemon grass or 4 strips lemon rind, thinly peeled

4 lemon or other citrus leaves

2 or 3 fresh whole chilies

1 tablespoon fish sauce

2 tablespoons lemon juice, or to taste

1 fresh red chili, seeded and sliced

2 tablespoons chopped coriander leaves

Shell and de-vein shrimps. Wash shrimps heads well, drain thoroughly. Heat oil in a saucepan and fry heads and shells of shrimps until they turn pink. Add hot water, salt, lemon grass or lemon rind, citrus leaves and whole chilies. Bring to the boil, cover and simmer for 20 minutes. Strain stock, return to the boil, add shrimps and simmer for 3-4 minutes or until shrimps are cooked. Add fish sauce and lemon juice to taste. This soup should have a pronounced acid flavor, so add sufficient lemon juice to achieve this. Serve in a large tureen or in soup plates, sprinkled with sliced chili, coriander leaves and spring onions.