Step 1: Preparing Your Mise en Place
- 1/3 cup Thai chile paste
- 5 stalks lemongrass
- 10 fresh kaffir lime leaves
- 6 to 8 pieces galangal (approx. 1/3" thick slices)
- 2 to 3 shallots, roughly chopped
- 1/2 tsp whole black peppercorns
- 4" piece seaweed (such as kombu or wakame)
- 6 to 8 cups mixed mushrooms*
To start, first prepare the Thai chile paste.
For the lemongrass, cut off and discard the (upper) darker green part and then slice the lemongrass in half. Using something heavy, like a pestle, bruise the lemongrass to release flavor.
For the kaffir lime leaves, fold in half and tear each leaf into 2 or 3 pieces (do not tear all the way through). This, too, is to release flavor.
For the galangal, note that the amount needed will depend on the age of the galangal and your personal preference. The fresher the galangal, the stronger the flavor. If substituting ginger, adjust according to your preference — although, finding galangal really is recommended.
For the mushrooms, it is best to use mild mushrooms, such as enoki, eryngii (king oyster), maitake (hen-of-the-woods), shimeji, and/or oyster mushrooms. Using a variety of these mushrooms adds layers of flavor to the soup and adds nice texture, as well as overall appearance to the final dish.
To prepare the mushrooms, clean and slice lengthwise into 1/4" thick pieces. For enoki mushrooms and shimeji mushrooms, simply cut off the bottom of the mushrooms and break up into smaller pieces.
Step 2: Making the Broth
- 12 cups water*
- 1 1/2 tsp sea salt, or to taste*
- 1 tsp palm or cane sugar, or to taste
- 1 fresh lime, cut in half
- 1 pint grape tomatoes, sliced in half lengthwise
*Note: Water is used here instead of stock, as the final broth should have a clean mushroom flavor to it, rather than a strong overall vegetable flavor.
To make the broth, add the lemongrass, kaffir leaves, galangal, shallots, peppercorns, seaweed, and water to a large pot and bring to a gentle boil.
Next, add the salt, palm sugar, and about half of the Thai chile paste. Reduce the heat to low and let the broth simmer for approximately 20 to 30 minutes, or until the liquid is flavorful and aromatic. As the broth cooks, taste it for seasoning and flavor — adding more salt and/or Thai chile paste as desired.
Once the broth is done, strain the liquid and discard the lemongrass, etc.
Next, pour the broth into a clean pot and bring to a gentle simmer. At this point, start adding the mushrooms — larger pieces first. Once all of the mushrooms have been added, turn off the heat. If the mushrooms are cooked too long, they can become chewy and shrink in size.
Lastly, add the fresh lime juice to taste. The amount depends on how sour you want the final soup to be. Keep in mind that guests can always add more during the meal, if desired.
Add the grape tomatoes just before service.
Step 3: Serving the Soup
- 1/2 bunch fresh cilantro, roughly chopped
- 8 to 16 red Thai chiles*
- 1 to 2 limes, sliced into wedges (for garnish)
For the Thai chiles, red chiles are used instead of green for their ripe fruitiness and color contrast. The amount needed will depend on how spicy you like your soup. To release more heat, split the chiles lengthwise, but leave them whole. For even more spice, lightly crush the chilies using the back of a knife or pestle.
To serve the soup, it is easiest to use a slotted spoon and remove some of the mushrooms from the broth. Place the mushrooms into the bottom of a warmed bowl and then add 1 or 2 chilies. Garnish the mushrooms with fresh cilantro and then ladle the hot broth over top. Serve immediately with additional cilantro and lime wedges.