Notes: If you can't find the fresh herbs, forget about them and use commercial Tom Kha paste instead, following the package instructions (if you're a vegetarian or vegan, read the label carefully as some brands contain chicken flavoring and fish sauce). Also, I use enoki mushrooms here, but feel free to use any mushroom you like. I caution against using shiitake mushrooms, however. I find them to be too strong for a delicate soup such as this. Oyster and white button mushrooms work fine. Portobello, on the other hand, tends to change the color of the broth from off-white to gray.
- 4 (8 ounce) packages fresh or frozen udon noodles
- 1 1/2 cups coconut milk
- 2 1/2 cups homemade or store-bought vegetable broth
- 2 stalks lemongrass, cut into 1-inch pieces and bruised
- 3 to 4 fresh kaffir lime leaves, torn and bruised
- 1/3 cup paper thin coins of fresh galangal
- 8 ounces fresh mushrooms, cut into bite-sized pieces (see note)
- 3 to 4 bird's eye chilies, sliced
- Kosher salt
- 1/4 cup juice from 3 to 4 limes
Prepare udon noodles according to package instructions; drain and set aside.
Place coconut milk, vegetable broth, lemongrass, kaffir lime leaves, and galangal in a 2-quart saucepan set over medium heat. Bring mixture to a very gentle boil; reduce heat so the liquid barely simmer. Allow the broth to infuse for 2 minutes.
Add mushrooms to the broth; adjust heat so mixture comes back to a gentle boil. Add prepared noodles to the pot; heat through. Remove pot from heat. Add sliced chilies while the soup is still hot. Season to taste with salt and 1/4 cup of lime juice. Adjust seasoning with more salt and lime juice as required, and serve immediately.