For the life of me, I couldn't find Kaffir lime leaves in any of the asian supermarkets, Whole Foods or Trader Joe's. Not sure, if there is a shortage or some other kind of issues. After looking for weeks, I decided to cook with substitutions for Kaffir lime leaves and finally found one that kinda worked. Galangal (or thai ginger) is also a bit tricky to find. I would definitely urge you to try and find galangal, but incase, you can't get one, you can substitute with ginger although the taste would vastly differ because galangal has more of a citrusy, eucalyptus type of flavor.
Tom Kha Soup is a spicy soup that originates from Laos and Thailand. Tom Kha, literally translated means 'boiled galangal' soup. The original recipe is known as Tom Kha Gai which is a chicken-based galangal soup. This soup has dominant galangal flavor in the coconut-based broth. There are several variations to the Tom Kha soup with vegan or vegetarian versions that use either Tofu (Tom Kha Taohu) or Mushrooms (Tom Kha Het). It is similar to Tom Yum soup except adding more coconut milk and reducing the amount of vegetable stock or water.
Personally, I think it is still debatable as to whether this soup is Tom Yum (or Yam) or Tom Kha Soup. Most recipes that I came across were using significant amount of coconut milk in both of these soups which makes it hard to conclude. Anyway, irrespective of what it's called, this spicy and flavorful soup is sure to please your taste buds.
1 stalk lemon grass
1 cup button (or shiitake) mushrooms, sliced (approx. 5-6 nos.)
1 1/2 - 2" piece galangal/thai ginger, thinly sliced
2 garlic cloves, minced
2 hot thai green chillies, finely chopped
3/4 - 1 tsp lime zest
3 tbsp low-sodium soy sauce
4 oz soft tofu (approx. 10-12 1" cubes)
3/4 cup bok choy, roughly chopped
1 bay leaf
4 1/2 cups water or vegetable stock
3/4 - 1 cup light coconut milk (adjust to taste)
1/2 - 1 tbsp lime juice (adjust to taste)
1/8 cup scallions, chopped (1 - 1 1/2 " long pieces)
1/4 cup fresh cilantro leaves, finely chopped
1 - 2 tsp raw sugar (adjust to taste)
To use lemongrass, cut off 2 inches of the lower bulb and discard the tough outer leaves. The pale yellow stalk can either be grated, sliced or crushed and used in the soup. If slicing, cut up to 2/3rd of the stalk until you get to the green and woody part of the stalk. The upper part of the stalk can be used in soups. The lemongrass is often crushed using a mortar and pestle to release the flavors. To know more about how to use lemongrass, check out the link.
To use galangal, wash the root, slice thinly and use as required.
Instead of kaffir lime leaves, I substituted it with 1 bay leaf and freshly grated lime zest.
Traditionally, thai bird's eye chilli is used in the soup. Since, I didn't have any, I used thai hot chillies which gave a good level of spice. You can also used crushed red pepper instead.
The choice of vegetables is based on the individual's preference. You can also add green or red bell pepper, broccoli, etc.,
Bring the water (or vegetable stock) to a boil and simmer for 5 mins (although I used vegetable broth, I would suggest using water for more depth of flavors).
Add the lemon grass, galangal, garlic, thai chillies, bay leaf and lime zest and boil on medium-low for 8-10 mins.
Filter the vegetable stock and discard the lemon grass, kaffir lime leaves and bay leaf (optional). Add carrots and cook for few mins until slightly soft.
Add bok choy and mushrooms and simmer for 2-3 mins.
Add tofu, soy sauce and sugar. Stir well and simmer for few mins. Add the coconut milk, if using, and boil for 4-5 mins.
Add the green part of the scallions and lime juice. Simmer for another 2-3 mins. Add chopped cilantro and boil for 1-2 mins.
Ladle into bowls and garnish with freshly chopped cilantro and serve hot.
Makes 3-4 servings.