Tom Yum Goong (Thai Hot and Sour Prawn Soup)

400 grams (14 oz.) medium-size prawns
3 stalks lemon grass
2 cloves garlic
2 tsp. chopped coriander root
4-6 pieces  peppercorn
½ inch (15mm.) knob fresh Kha (Siamese ginger)
2 fresh red chilies
4 small fresh green chilies
6½ c. chicken stock
4 Khaffir lime leaves (Makrood)
⅓ cup vegetable oil
2 tbsp. fish sauce (patis)
2 tbsp. lime sauce (dayap)
Freshly shredded coriander leaves

Shell and devein the prawns, leaving the tails intact.  Retain the heads and shells.  Cut the lemon grass into short lengths, approximately 1 inch and pound lightly with the back of the knife.  Place the garlic coriander root and peppercorn in a mortar and pound into a smooth paste.  Slice the ginger, cut the chilies into very tiny rings and shred the lime leaves.

Heat the oil in the sauce pan, add the prawn heads and shells and stir-fry for 3-4 minutes.  Then add chicken stock and bring to a boil.  Cover the pan, reduce the heat and simmer for 10 minutes.  Pour the stock through a fine strainer into a fresh saucepan and bring back to the boil.

Stir in the spice-paste and add the lemon grass, ginger, lime leaves and prawns.  Bring back to boil and allow to cook for approximately 3 more minutes.