Hot and sour Thai soup is a recipe signaled at our house by fresh watercress at the market. I always jump on making this incredible, fragrant, and warming soup then. The combination of tangy, floral, savory, and spicy flavors is truly mouth-watering.
The soup from our local Thai food truck that inspired this recipe is fiendishly hot. However, I have tailored this hot and sour soup so that no one will miss out.
It's served with fresh Thai chili and vegan fish sauce on the side, so everyone can enjoy this fabulous traditional Thai soup exactly to taste.
🌶 Thai seasonings
- Makrut Lime Leaf - You may know this unique seasoning by the name kaffir lime. I prefer to use Makrut or Thai lime out of cultural sensitivity. Modern Farmer has an easy-to-understand explanation of why the word kaffir is hurtful and offensive. Botanically it is citrus hystrix and has an intense flavor to its leaves and rind.
- Galangal - Is a cousin to ordinary ginger. However, like Makrut lime, it is so unique that there just isn't any substitute. It's floral and very spicy. One way to tell galangal from ginger is the mature roots are fibrous and harder to slice than common ginger. Take a little bite, and no doubt its perfume and lingering heat will impress you.
- Vegan Fish Sauce - More and more grocers are stocking fish sauce alternatives for vegetarians. If you want the best, though, try my Vegan Fish Sauce recipe. It has a deep, rich flavor and no artificial additives.
- Chili flakes - Use more or less to your taste, and any variety will do.
- Lemongrass - Choose fresh lemongrass. While dried lemongrass makes a nice tea, it won't have the impact or delicacy that makes hot and sour Thai soup so fragrant and mouthwatering.
- Coconut Sugar - Coconut sugar has the advantage of being less processed than refined brown sugar and has a natural dark caramel flavor.
- Tamarind Paste - Tamarind paste is naturally sweet and sour with its own characteristic taste. Select whole "seedless" tamarind sold in blocks. If you use the sort of tamarind puree or concentrate sold in jars, you'll want to start with half the amount and add more to taste.
It is a little ironic that watercress is the one ingredient in this recipe that I have a hard time getting hold of. That's because fresh Thai seasonings are common right where I live, but watercress is seasonal.
Do you have watercress where you live? I am guessing it may be easier to find than the fresh Makrut lime leaves or galangal that grow in our community garden.
I hope you will be able to find the spices you need in farmers' markets or ethnic markets in your area. They are essential for this authentic hot and sour Thai soup.
🍵 Making the broth
Making the deeply flavored broth for this incredible recipe begins with preparing lemongrass.
Want a tip on preparing lemongrass? Smash the bulb end of the stalk before chopping it coarsely. This releases natural oils to add more flavor.
The rest of the broth ingredients are prepped quickly. Simply tear Makrut lime leaves in half, slice galangal thin, coarsely chop onion, and add it to a pot with tamarind paste, coconut sugar, chili flake, salt, and vegan fish sauce.
💭 What can I substitute?
To make this delicious soup at its best, you'll need to know which ingredients you can substitute successfully and which you can't.
In my book, Makrut lime, galangal, lemongrass, and tamarind have no substitutes. They are remarkable seasonings and worth seeking out. Thus, as you can guess, they can't be swapped out or replaced in this recipe.
Peppery watercress and sweet juicy tomatoes are vegetables you also won't want to change.
Substitutes that work
King oyster mushrooms have a marvelous meaty texture, but you can use whatever type of mushroom you have available.
Likewise, you can substitute other brown sugars for coconut sugar, and your onions can be white, red, or yellow.
The tofu you select can be any grade from medium to extra-firm as long as it's not silken type.
If you aren't able to find or make vegan fish sauce, you can substitute soy sauce with a little toasted sesame oil added to it. Try ⅛ teaspoon of sesame oil for every tablespoon of soy sauce. It won't be the same or quite as good, but this combination provides a different flavor that is tasty on its own.
👩🏻🍳 Expert tips
- Saute onion, mushroom, lime leaves, and galangal until fragrant and just lightly browned.
- Wait until just before serving soup to add tomato wedges and watercress.
- Serve hot and sour Thai soup piping hot with sliced chilis and vegan fish sauce on the side.
I am excited for you to try my hot and sour Thai soup. Just wait until you bite into its plump tofu, chewy mushrooms, and juicy vegetables. Let me know what ingredients are common to where you live and how many you were able to find!
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Hot and Sour Thai Soup
- 1 large stalk lemon grass
- 2 whole Makrut lime leaves
- 3 inch piece galangal
- 2 cups coarsely chopped yellow onion
- ¼ tsp. red chili flake to taste
- 1 TB coconut palm sugar
- 1 TB tamarind paste
- 1 tsp. sea salt
- 1 TB Vegan Fish Sauce
- 4 cups water
Vegetables and Tofu
- 10 oz. medium firm tofu
- ⅔ cup tomato wedges
- 2 cups watercress leaves
- 1 TB plain oil
- 1 cup coarsely chopped mushrooms, king oyster preferred
- 1 cup yellow onion, cut in wide petals
- 2 whole Makrut lime leaves
- 4 thin slices galangal
- Sliced red and green Thai chilies to taste
- Sliced red and green Thai chilis to taste
- Vegan fish sauce
- Smash the bulb end of the lemongrass and cut the stalk into four pieces. Slice galangal. Tear Makrut lime leaves in half.
- Place prepared lemongrass, galangal and lime leaves in a soup pot with the remaining stock ingredients. Bring to a boil and cook at low heat for 10 minutes while preparing tofu and vegetables for soup.
- After 10 minutes, pour the stock through a strainer to separate the broth from seasonings. Toss seasonings out and return broth to soup pot.
Vegetables and tofu
- Cut tofu into one-inch cubes and set it aside with tomato wedges and watercress.
- Heat oil in a saucepan. Saute onion, mushroom, lime leaves, and galangal until fragrant and just lightly browned.
- Add onion and mushroom mixture to soup broth along with the tofu. Bring to a boil.
- Gently stir tomato wedges and watercress into the soup. Cover with a lid and remove the pot from the heat.
- Slice fresh red and green Thai chilies and place them on the table with Vegan Fish Sauce or soy sauce.
- Pour hot soup in bowls and let diners garnish with chili and sauce as desired.