Purple Yam Soup Recipe: Cambodian Shrimp Soup

Overhead view of purple yam soup with shrimp in a bowl, garnished with green onion. — Purple yam gives this Cambodian shrimp soup its soft color and gentle thickness.

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Purple yam soup is one of those quiet Cambodian bowls that does not need to announce itself. Grated purple yam melts into the water and turns the broth a soft, natural lavender color. The texture becomes gently thick, almost velvety, without any cream or thickener.

Shrimp brings a clean sweetness that balances the earthy yam. Fish sauce and a little sugar round out the flavor, and fresh green onion and basil go in at the very end so they stay bright. It is a simple one-pot soup that feels both comforting and light.

If you enjoy shrimp-based Cambodian soups, you might also like our Shrimp and Taro Root Soup, which uses a similar starchy vegetable to build body.

What You Need

The most important ingredient here is the purple yam. Look for one with rough brown skin and vivid purple flesh. Some markets sell it already grated and frozen, which saves time and works just as well.

Shrimp should be peeled, deveined, and finely ground or chopped so it distributes evenly through the soup. Fish sauce provides the main saltiness, and a small amount of sugar softens its edge.

If you are new to cooking with purple yam, do not worry about the color bleeding into the water. The Centre for Food Safety explains that the purple pigment is a natural plant compound called anthocyanin and is safe to eat.

Equipment

Soup pot: To boil the water and cook the yam and shrimp.
Chef’s knife: To chop the green onion and sweet basil.
Cutting board: To hold the herbs while chopping.
Grater: To grate the fresh purple yam if you are not using the frozen kind.
Measuring cup: To measure the 4 cups of water.
Measuring spoons: To measure the salt, black pepper, and sugar.
Mixing bowl: To season the ground shrimp before cooking.
Wooden spoon: To stir the soup, especially after the yam goes in, so it does not stick.
Ladle: To serve the finished soup into bowls.

How to Make Purple Yam Soup

Step 1: Season the Shrimp

In a small bowl, combine ½ lb (225 g) peeled, deveined, and ground shrimp with ½ teaspoon salt, ¼ teaspoon black pepper, and half of the chopped green onion. Mix well and set it aside.

Step 2: Boil the Water

Pour 4 cups of water into a soup pot and set it over high heat. Let the water come to a rolling boil.

Step 3: Cook the Purple Yam

Add 2 cups of fresh grated purple yam, or one package of frozen grated purple yam, to the boiling water. Stir well. Cook until the yam is tender and the broth begins to thicken, stirring occasionally so the yam does not settle on the bottom.

Step 4: Add the Shrimp

Add the seasoned shrimp to the pot. Stir well and cook until the shrimp turn a darker pink color and are cooked through.

Step 5: Season and Finish

Season the soup with 2 tablespoons fish sauce and 1 teaspoon sugar. Stir and taste. Top with the remaining green onion and ⅓ cup chopped sweet basil leaves, if using. Serve hot.

Cooking Tips

Keep an eye on the pot after adding the grated yam. It releases starch and can stick to the bottom if you do not stir it every few minutes.

Taste the broth before adding more fish sauce. Different brands vary in saltiness, and the shrimp is already seasoned.

Frozen grated purple yam does not need to be thawed first. Add it directly to the boiling water and adjust the cooking time slightly if needed.

How to Serve

Ladle the soup into bowls and serve it hot. It works well with steamed jasmine rice on the side, or on its own as a light meal. For another quick shrimp soup, try our Shrimp with Yu Choy Soup.

Recipe Notes

Purple yam is sometimes confused with purple sweet potato or ube. True purple yam has rough, bark-like brown skin and a drier, starchier texture. If you cannot find fresh purple yam, the frozen grated version is the closest substitute.

For another Cambodian soup that uses a starchy vegetable to thicken the broth, see our White Yam with Pork Soup.

Frequently Asked Questions

What does purple yam soup taste like?

The broth is mildly sweet from the yam and shrimp, with a savory base from fish sauce. It is not spicy or sour. The texture is thick and soft, similar to a light porridge.

Can I use frozen grated purple yam?

Yes. Add the frozen grated yam directly to the boiling water. Stir well and cook until tender. You may need a few extra minutes compared to fresh yam.

How should I store leftovers?

Store the soup in a covered container in the refrigerator for up to 2 days. Reheat gently on the stovetop or in the microwave. The broth will thicken more as it sits; add a splash of water when reheating if needed.

Final Thoughts

This purple yam soup is a good reminder that Cambodian home cooking does not need many ingredients to feel complete. The yam does most of the work, turning water into a soft, satisfying broth. Serve it hot with rice, and adjust the fish sauce to your taste.