# Hot and Sour Soup

Hot and sour soup is a Chinese favorite: a thick, savory broth with mushrooms, tofu and egg, made tangy with vinegar and warm with white pepper. It is quick to make at home and cheaper than takeout.

The heat comes from white pepper, not chili, and the sourness from vinegar added at the end. Adding the vinegar off the heat keeps its flavor sharp and clean.

- Total time: 40 min (prep 20 min, cook 20 min)
- Serves: 6
- Per serving (estimated): 170 kcal, 14 g protein
- Cuisine: Chinese. Category: Soup. Diet: dairy-free, high-protein.

## Ingredients

- 6 cups chicken broth
- 200 g pork loin, cut into thin strips
- 8 dried shiitake mushrooms, soaked 20 minutes and sliced
- 1 can (225 g) bamboo shoots, drained and sliced
- 200 g firm tofu, cut into thin strips
- 3 tbsp soy sauce
- 1 tbsp grated fresh ginger
- 1/3 cup rice vinegar
- 1 tbsp Chinkiang black vinegar
- 1 tsp ground white pepper
- 1 tsp sugar
- 3 tbsp cornstarch
- 1/4 cup cold water
- 2 large eggs, beaten
- 1 tsp toasted sesame oil
- 3 scallions, thinly sliced

## Method

1. Soak the dried shiitake in hot water for 20 minutes, then slice, keeping the soaking liquid. Strain it through a paper towel into the broth to remove grit.
2. Toss the pork strips with 1 tbsp soy sauce and 1 tsp of the cornstarch. Let sit 10 minutes.
3. Bring the broth, ginger and mushrooms to a simmer in a large pot. Add the pork and stir to separate. Simmer 3 minutes, until cooked through (145°F, 63°C).
4. Add the bamboo shoots, tofu, remaining 2 tbsp soy sauce, sugar and white pepper. Simmer 5 minutes.
5. Whisk the remaining cornstarch with the cold water until smooth. Stir it into the soup and cook 1 to 2 minutes until glossy and slightly thick.
6. Lower the heat to a gentle simmer. Pour in the eggs in a thin stream while stirring slowly, so ribbons form.
7. Turn off the heat. Stir in the rice vinegar, black vinegar and sesame oil. Adding vinegar off the heat keeps its tang.
8. Taste: it should be sour, peppery and savory. Add more vinegar or pepper to taste and top with scallions.

## Why it works

- Marinating the pork with cornstarch protects it, so the thin strips stay tender in the hot soup.
- Dried shiitake and their soaking liquid add deep, meaty umami to the broth.
- A cornstarch slurry gives the soup its slightly thick, glossy body and holds the egg in ribbons.
- Adding vinegar off the heat preserves its bright tang, which would fade with long cooking.

## The science

- **Velvet the pork.** Coating thin meat strips in a little cornstarch before cooking forms a protective layer. It helps lock in moisture and keeps the pork tender in hot liquid. This simple trick, called velveting, is why restaurant soups have such soft meat.
- **Heat from pepper, tang from vinegar.** White pepper has a sharp, earthy heat from piperine, which differs from the burn of chili. Vinegar gives the sourness, and its aroma fades with long heating. Adding both near the end, and tasting, lets you balance the soup exactly to your liking.

## Tips

- Add the vinegar and pepper at the end and adjust, since brands differ in strength.
- Pour the egg slowly in a thin stream for delicate ribbons.
- Slice the tofu, mushrooms and bamboo shoots into thin matching strips so every spoonful is even.

## Mistakes to avoid

- Boiling after the vinegar goes in: the tang fades, so add it off the heat.
- Dumping the slurry in without stirring: it clumps, so pour while stirring.
- Using black pepper instead of white: the flavor is different, so use white pepper for the classic taste.

## Variations and swaps

- Make it vegetarian with vegetable broth and extra mushrooms in place of the pork.
- Use shredded chicken or shrimp instead of pork.
- Add a spoonful of chili oil at the table for more heat.
- Swap Chinkiang black vinegar for balsamic vinegar, which is sweeter and a little less complex.
- Swap pork loin for chicken breast, cut into thin strips.

## Storage

Refrigerate within 2 hours for up to 3 days. Reheat to 165°F (74°C), stirring, and refresh with a splash of vinegar if the flavor has dulled.

## FAQ

**What gives hot and sour soup its flavor?**

The sour comes from rice and black vinegar, and the heat comes mainly from white pepper. Mushrooms, soy sauce and sesame oil add savory depth.

**Is hot and sour soup spicy?**

It is peppery rather than fiery. You can add chili oil to turn up the heat.

**Can I make hot and sour soup vegetarian?**

Yes. Use vegetable broth and swap the pork for extra mushrooms or tofu, which keeps it rich and savory.

**Where can I find wood ear mushrooms?**

You can find dried wood ear at Asian grocery stores. They are optional, and extra shiitake works fine in their place.

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