Key to this dish is acquiring a small amount of galangal (kha) instead of ginger as most recipes specify. Galangal, also known as “blue ginger” or “Thai ginger,” is a rhizome (Alpinia galanga) in the same botanical family as ginger but with slightly different characteristics. It is more red-orange than ginger and much more woody — tough and inedible, in fact — and the flavor is a bit more peppery and less sweet than fresh ginger. Finding a source for genuine galangal can make a big difference in the flavor of this soup.
Other than galangal, the only essential components are whole lemongrass and kaffir lime leaves but both of these can weather substitutions. As an herb, dried lemongrass is much easier to locate, and fresh limes can provide a similar flavor as the kaffir leaves themselves. Likewise, most any mushroom species can be used.
Sambal oelek chili paste breaks the truest authenticity of this soup, but some chile heat should be expected. Chili oil or fresh red Thai chile peppers can be used and adjusted for personal preference.
For a traditional Thai flavor, fresh cilantro is included to finish; for a more Laotian spin, use fresh dill.
Tom Kha Gai
1½ lb chicken (thigh meat)
8 oz shiitake mushrooms
4 green onions
2-in piece of galangal
6 c chicken stock
13.5-oz can of coconut milk
2 T fish sauce
1 t sugar
1 t lemongrass
1 T sambal oelek
1 Peel the galangal and cut it into large chunks. Zest and juice one entire lime.
2 Bring the stock to a boil and add the galangal, lemongrass and lime zest. Reduce the heat and simmer, uncovered, for 10 min. Strain the stock into a clean pot.
3 Roughly cut the chicken and mushrooms into bite-sized pieces and add to the pot. Return the soup to a boil then reduce the heat and simmer, covered, for about 25 min.
4 Chop the cilantro and onions and add along with the coconut milk, fish sauce, sambal oelek and sugar. Finish with chili oil and fresh lime juice to taste.