Thailand's culinary heritage, like most of its South-east Asian neighbors', is one that is based on hundreds of years of tradition, culture and the abundant availability of some of the world's most exotic ingredients. One of the most famous of Thai dishes in the Western world is the refreshingly hot and sour Tom Yam Gung soup. It is the quintessential Thai dish, containing all the flavors that is unique to that country's cuisine. The balance of saltiness, sourness and heat really brings this soup to a whole new level.
In Thai, tom means boil and yam means mix while gung stands for shrimp. A light soup that is usually served with fragrant steamed jasmine rice, tom yam gung is traditionally made with seafood, specifically shrimp. In fact, the base of this soup is produced by boiling shrimp heads and shells to obtain the delicious flavor. A word of advice, do not even attempt to make this soup if you can't purchase shrimp with their heads still intact because the head is where you get the most flavor out of the shrimp.
Apart from the shrimp, here is what else you will need in order to make this soup: fish sauce, 1-2 stalks of lemongrass, 3-4 bird's eye chilies (the tiny but explosively spicy chili) and lime zest and juice. The recipe actually calls for kaffir lime leaves but it is a hard ingredient to track down and can usually be substituted with regular lime zest. To add bulk to the soup, I also added baby corn and sliced carrots. The only part of the lemongrass that is usable is the white portion, starting from about 6 inches from the end. Cut the very end part of the root and the rest of the green portion off. Peel the outer one or two layers of the remaining part of the lemongrass and cut it into approximately 1-inch sections so that they can be easily removed after cooking. Use the side of your knife and press hard onto the lemongrass, effectively bruising it and releasing its flavor and smell. As for the bird eye chili, just slice them into thin pieces.
Start by adding some salt to a pot of water and boiling the heads and shells of the shrimp for about 20 minutes (any longer and the resulting stock could become bitter from the release of calcium from the shells). Strain the shells from the stock and bring the stock to a boil again, adding fish sauce, lemongrass, lime zest and chilies. Next add the peeled but uncooked shrimp and also the carrots and baby corn and let the soup simmer and cook. When everything is cooked, season the soup again by adding fish sauce, lime juice and salt (remember to taste it first!). Finally, garnish it with cilantro leaves just before serving.