# Thai Tom Yum Soup

Tom yum is a famous Thai hot and sour soup with shrimp, mushrooms, lemongrass and plenty of lime. It is fragrant, bright and ready in about 40 minutes.

The soup depends on a few fresh herbs: lemongrass, galangal and makrut lime leaves. Simmer them gently to build the aroma, then finish with lime juice off the heat so the sourness stays fresh.

- Total time: 40 min (prep 20 min, cook 20 min)
- Serves: 4
- Per serving (estimated): 210 kcal, 22 g protein
- Cuisine: Thai. Category: Soup. Diet: dairy-free, gluten-free, high-protein.

## Ingredients

- 5 cups chicken or shrimp stock
- 2 stalks lemongrass, bruised and cut into 5 cm pieces
- 5 slices galangal (or ginger)
- 5 makrut lime leaves, torn
- 3 Thai chilies, bruised
- 250 g mushrooms, halved (straw or button)
- 2 medium tomatoes, cut in wedges
- 400 g large shrimp, peeled and deveined
- 2 tbsp fish sauce
- 1 tbsp Thai chili paste in oil (nam prik pao)
- 3 tbsp lime juice
- 1 tsp sugar
- 1/4 cup cilantro leaves
- 1 shallot, thinly sliced

## Method

1. Bring the stock to a boil in a medium pot. Add the lemongrass, galangal, lime leaves and Thai chilies.
2. Lower the heat and simmer gently for 10 minutes, until the broth smells strongly of lemongrass and lime.
3. Add the shallot, mushrooms and tomatoes. Simmer 4 minutes, until the mushrooms soften.
4. Stir in the fish sauce, chili paste and sugar.
5. Add the shrimp and cook 2 to 3 minutes, just until they turn pink and curl into a loose C shape, and reach 145°F (63°C) if you check.
6. Turn off the heat. Stir in the lime juice and cilantro. Adding it off the heat keeps the lime flavor bright.
7. Taste: it should be sour, salty, spicy and slightly sweet. Add more lime, fish sauce or sugar to balance.
8. Serve hot. Eat around the lemongrass, galangal and lime leaves, which are for flavor and not for eating.

## Why it works

- Bruising the lemongrass and chilies releases their oils so they flavor the broth faster.
- Simmering the aromatics gently infuses the stock with citrusy, floral flavor without turning it bitter.
- Shrimp added at the end cook in minutes, so they stay tender and sweet.
- Fish sauce, lime, chili and sugar are balanced at the end so each flavor is clear.

## The science

- **Aromatic herbs and oil.** Lemongrass, galangal and lime leaves carry their aroma in tiny oil droplets inside the plant cells. Bruising or tearing them breaks those cells open. A gentle simmer then pulls the oils into the broth, where they give a fragrant, citrusy flavor.
- **Fish sauce adds umami.** Fish sauce is made from fermented fish, so it is rich in glutamate and salt. It gives the broth a savory depth that salt alone cannot. Add it in small amounts and taste, then balance it with lime for sourness and a little sugar.

## Tips

- Bruise the lemongrass with the back of a knife before slicing so it releases its aroma.
- Add the lime juice off the heat, since boiling dulls its brightness.
- Taste and balance at the end: adjust lime, fish sauce and sugar until it tastes vivid.

## Mistakes to avoid

- Boiling the soup hard after adding the lime juice: the flavor turns dull, so add lime at the end.
- Overcooking the shrimp: they turn rubbery, so take it off the heat as soon as they curl and turn pink.
- Using too little lemongrass: the soup tastes flat, so use 2 full stalks.

## Variations and swaps

- Make it creamy tom yum by stirring in 1/2 cup evaporated milk or coconut milk.
- Use chicken or tofu in place of the shrimp.
- Add glass noodles to make it a full meal.
- Swap galangal for fresh ginger, which is more pungent and less piney.
- Swap makrut lime leaves for the zest of 1 lime plus extra lime juice.

## Storage

Refrigerate within 2 hours for up to 2 days, because shrimp turn rubbery when stored longer. Reheat gently to 165°F (74°C) without boiling.

## FAQ

**What does tom yum soup taste like?**

Tom yum tastes hot, sour, salty and slightly sweet, with a citrusy, herbal aroma from lemongrass and lime leaves.

**What is the difference between tom yum and tom kha?**

Tom yum is a clear, sour and spicy broth, while tom kha is creamy with coconut milk and milder in heat.

**Can I make tom yum without galangal?**

Yes. Use fresh ginger instead, which has a similar warmth with a slightly different flavor.

**Do you eat the lemongrass in tom yum?**

No. Lemongrass, galangal and lime leaves are tough and are there for flavor, so you eat around them.

---
Source: https://cookingscientist.com/recipes/tom-yum-soup (Cooking Scientist). Learn the science of cooking in the Cooking Scientist app for iPhone and iPad: https://apps.apple.com/app/id6830326846