Vietnamese Opo Squash Soup with Pork

Vietnamese opo squash soup is a light, savory soup of tender gourd simmered with ground pork, fish sauce, and fresh herbs. Often served as part of a home-style Vietnamese meal, it is simple to make and lets the squash’s mild, gently sweet flavor shine. Recipes vary by household; this version uses pork for a quick, flavorful broth.

Ingredients

4 cups (500 g) peeled, sliced opo squash, cut into pieces about ¼ inch (6 mm) thick
8 oz (225 g) ground pork
⅓ cup (50 g) finely chopped shallot, or yellow onion
1 teaspoon (5 ml) neutral cooking oil
6 cups (1.4 L) water
1 tablespoon (15 ml) fish sauce, plus more to taste
½ teaspoon (3 g) fine salt, plus more to taste
¼ teaspoon (0.5 g) freshly ground black pepper
½ cup (25 g) thinly sliced green onion, divided
¼ cup (10 g) roughly chopped cilantro leaves and tender stems

Instructions

Prepare the squash. Rinse the opo squash and trim off both ends. Peel it with a vegetable peeler; if the skin is very thin and tender, you can leave it on after washing, though peeled squash gives the soup a softer texture. Cut the squash lengthwise and check the center. Leave small, tender seeds in place, but scoop out any large, firm seeds. Slice the squash into pieces about ¼ inch (6 mm) thick so they cook evenly. Chop the shallot, slice the green onion, and chop the cilantro.
Season the pork. Put the ground pork in a bowl with the shallot, ½ tablespoon (7 ml) of the fish sauce, the salt, and the black pepper. Mix with a fork or clean hands just until evenly combined. Avoid kneading it into a paste; lightly mixed pork breaks into tender, distinct pieces in the soup.
Start the broth. Heat the oil in a medium pot over medium heat. Add the seasoned pork and cook for about 4 to 5 minutes, breaking it into small pieces with a spoon. Stir as it cooks so the shallot softens and the pork cooks evenly. Check several of the largest pieces with an instant-read thermometer; ground pork should reach the USDA FSIS safe minimum internal temperature of 160°F (71°C). If a piece has not reached that temperature, continue cooking and check again.
Simmer the soup. Pour in the water and raise the heat until the liquid reaches a steady boil, skimming off any gray foam if you want a clearer-looking broth. Stir in the remaining ½ tablespoon (7 ml) fish sauce and half of the green onion. Lower the heat and simmer for 3 minutes to let the pork flavor the broth.
Cook the squash until just tender. Add the sliced opo squash and bring the soup back to a gentle simmer. Cook uncovered for 10 to 12 minutes, stirring once or twice, until the squash is tender when pierced but still holds its shape. Thin slices may finish sooner; thicker pieces may need another minute or two. Avoid a hard boil, which can break up the squash and make the broth cloudy.
Adjust and serve. Taste the broth. Add fish sauce for savory depth or a small pinch of salt if it tastes flat; the amount needed depends on the saltiness of your fish sauce. Turn off the heat and stir in the remaining green onion and cilantro. Ladle the soup into bowls and serve hot.

Tips

Choose a firm squash. Look for opo that feels heavy for its size and has unblemished skin. A very large squash may have a spongier center and hard seeds, so remove those before slicing. If the squash is especially watery, use the same amount by weight and avoid adding extra water.
Keep the slices even. Pieces of similar thickness cook at roughly the same pace. If you cut the squash into chunks instead of thin half-moons, allow extra simmering time and test the largest piece before serving.
Balance the broth gradually. Fish sauce brands differ in saltiness. Start with the stated amount, taste after the squash is cooked, and add more in small increments. If the soup becomes too salty, add a little hot water and taste again rather than adding sugar, which changes the broth’s character.
Use a substitute thoughtfully. If opo squash is unavailable, peeled chayote is the closest easy swap and has a similarly mild flavor, though it may take a few extra minutes to turn tender. Zucchini works too, but cooks faster and becomes softer, so add it near the end.

Serving Suggestions

Serve this soup hot in small bowls alongside steamed jasmine rice and a main dish such as grilled fish, sautéed greens, or caramelized pork. In a Vietnamese family-style meal, the soup can be shared at the table with rice and several other dishes rather than treated as a large starter. Its mild broth is a useful counterpoint to salty, savory, or spicy foods.

For a simple one-bowl meal, spoon rice into a bowl and ladle the soup over or beside it. Put extra fish sauce and sliced fresh chile on the table so each person can season their own serving. A squeeze of lime is not essential and is not traditional in every version, but a small amount can brighten the broth if you enjoy a sharper flavor. Add it at the table, not to the whole pot, so the soup remains balanced for everyone.

Variations

Make it with shrimp: Replace the ground pork with 8 oz (225 g) peeled, deveined raw shrimp. Season them lightly with fish sauce and pepper, then add them to the simmering broth shortly before the squash is done. Cook until opaque and check that the thickest shrimp reaches 145°F (63°C), the USDA FSIS safe minimum for fish and seafood. Shrimp cook quickly, so avoid leaving them simmering for the full squash cooking time.

Make it vegetarian: Skip the pork and use 1 tablespoon (15 ml) oil to soften the shallot, then add the water and squash. For more savory flavor, simmer 4 oz (115 g) sliced shiitake or cremini mushrooms in the broth. Replace fish sauce with 1 to 1½ tablespoons (15 to 22 ml) soy sauce, starting with less and adjusting to taste. The result will have a lighter, less pork-rich broth; use a vegetable broth instead of water if you want a fuller flavor.

Add dried shrimp: For a more pronounced seafood savoriness, soak 1 tablespoon (8 g) dried shrimp in warm water for 10 minutes, drain, and chop finely. Cook it with the shallot before adding the pork. Dried shrimp can be salty, so reduce the initial salt and adjust only after simmering.

Change the herbs: Cilantro and green onion are a fresh, familiar finish, but you can use just green onion or add a little chopped Vietnamese coriander if it is available. Vietnamese coriander (rau răm) has a peppery, herbal taste; it is not the same as cilantro, so use a smaller amount at first. Stir delicate herbs in after turning off the heat.

Storage and Reheating

Cool leftovers promptly and refrigerate them within 2 hours of cooking, preferably in shallow, covered containers. The soup keeps for 3 to 4 days in the refrigerator. The squash will soften as it sits, so the texture is best in the first couple of days, but the broth remains suitable for reheating throughout the storage period when handled safely.

Reheat only the portion you plan to eat, either in a saucepan over medium heat or in a microwave-safe bowl, stirring occasionally so it warms evenly. Bring leftovers to 165°F (74°C), checking with a food thermometer. If the soup has thickened or the squash has absorbed some broth, add a splash of water while reheating and correct the seasoning afterward.

For longer storage, freeze the cooled soup in airtight freezer-safe containers for up to 2 to 3 months for best quality. Leave a little space at the top for expansion. Thaw overnight in the refrigerator and reheat to 165°F (74°C). Freezing is safe, but the squash may become softer or slightly grainy after thawing; if texture matters, freeze the pork broth separately and cook fresh squash when serving.

Frequently Asked Questions

What is opo squash?
Opo squash, also called bottle gourd or calabash, is a long, pale green gourd with mild-flavored flesh. It is sold in many Asian grocery stores and some larger supermarkets. Choose one that feels firm and heavy, and peel it if the skin is thick or tough.

Can I use a different kind of squash?
Yes. Chayote is the closest substitute for its mild flavor and firm texture. Zucchini is easier to find but softens more quickly, so add it during the final 5 to 7 minutes of simmering and stop cooking as soon as it is tender. Butternut squash is much sweeter and firmer, so it will make a noticeably different soup and needs longer cooking.

Do I need to use stock?
No. Water works well because the pork, shallot, and fish sauce season the broth as they simmer. If you prefer stock, choose a mild, unsalted pork or chicken stock and reduce the added salt and fish sauce until you have tasted the finished soup. Strongly flavored stock can overwhelm the delicate squash.

Why did my opo squash turn mushy?
It was likely sliced very thin, simmered too long, or cooked at a vigorous boil. Cut even pieces about ¼ inch thick, keep the soup at a gentle simmer, and begin checking for tenderness after 10 minutes. The squash should yield to a fork but still hold together when lifted with a spoon.

Can I make the soup ahead?
Yes. You can make it up to a day ahead and refrigerate it promptly, but the squash will continue to soften while stored. For the firmest texture, prepare the pork broth in advance, chill it, then bring it to a boil and add freshly cut squash shortly before serving. Reheat any prepared soup to 165°F (74°C).

Is fish sauce essential?
Fish sauce gives the soup its characteristic savory seasoning, but it is not the only option. For a fish-free version, use soy sauce or a vegetarian fish sauce alternative, adding it gradually because the salt levels vary. The flavor will be different, but the soup will still pair well with the mild squash and herbs.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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