Put 2 soupbowlfuls (1½ pints) of water in a pot and add the crushed lemon grass, the knotted spring onions, the washed rice, the sprigs of coriander and some salt. When the water boils (the pot having been put on the fire), add the pieces of deer meat and sprinkle some fish sauce on top. Let it go on cooking over a low fire until the meat is tender and the liquid has reduced. Add the phak i leut leaves. Taste, and check the saltiness. Take out the pieces of deer neck and separate the bones from the meat; then return the pieces of meat to the pot. (If some of the pieces are large, cut them into smaller bite-size pieces.)
Transfer the soup to a large bowl and garnish it with the chopped spring onion leaves. Serve it with Lap Sin Fahn (Venison lap—see recipes 25 and 41 for the method of making a lap).