These Dried Worms Make Pho Taste Great

A couple months ago, I received an email from a chef named Cyrus Phan, who described himself as a “recreational importer” of specialty foods. He offered to send over a bag of dried peanut worms—called sa sung in Vietnamese—for me to experiment with, and he noted the worms are something of a secret ingredient for pho broth. After I gave him our usual spiel about how we only accept samples with the understanding that we aren’t obliged to write about them in any way, I said, “Sure! Send me dried worms!”

I had heard about them before; the first time I read about them was on Andrea Nguyen’s website, Viet World Kitchen, in a 2011 post titled “Pho Secret Ingredients: Dried Earthworms (Sa Sung).” At that point, I had been trying to recreate a specific bowl of pho I had grown up eating in Hong Kong, and reading about sa sung, an ingredient that was entirely unavailable in the United States, made me feel wonderful about my many, many failed attempts. It wasn’t that I was bad at making pho, I just needed some worms.

Nguyen went on to write more about sa sung in her phenomenal book The Pho Cookbook: Easy to Adventurous Recipes for Vietnam’s Favorite Soup and Noodles, for which she won a James Beard Award in 2018, including not just how to prepare them but also how to find substitutes. I planned on following her advice when I got my hands on the product Phan had promised to send over.

What arrived in the mail was a bag of what looked like ribbed finger cots—which is, of course, just another way of saying mini condoms—had been left out in the rain for a couple days and then set in a dusty shed to dry. I opened the bag and took a sniff. The aroma was pretty similar to other dried sea products, leaning more toward the heady sweetness of dried squid and cuttlefish than the broadly oceanic smell of, say, dried shrimp or finfish.

I decided to make an initial foray into worm-flavored pho by including a handful of toasted sa sung in Kenji’s pressure cooker chicken pho recipe. The resulting broth was extremely tasty, though the difference the sa sung made was hard to describe; the broth was at once a little sweeter and even more savory, maybe, but also something else that I couldn't put my finger on.

I decided to probe more deeply.

What Are Sa Sung?

Nguyen’s site has a concise explanation of what the worms are, and it appears that a lot of other online sources plagiarize her copy, which we, of course, will not do here. I urge you to visit that page for her description (also, it’s an excellent web site!).

In brief, sa sung are known as Sipincula nudus or, more commonly in English, "peanut worms," due to the appearance of their ridged exteriors when the worm is not extended. They're marine worms that are eaten both fresh and dried, although it is only the dried form that is used to flavor broth in Vietnam. (They're also considered a delicacy in China, and, like other Chinese delicacies, are fodder for gawking expats to write about in their hometown paper.) The worms are harvested in tidal flats, often by women, according to this article in Tuoi Tre News, the largest daily newspaper in Vietnam, and a kilogram of worms can be sold for around $15 (that article has some lovely photos of the worms in their fresh form, although they may not be for the worm-averse).

I called up Nguyen, and she noted that while sa sung are considered an ingredient that is more commonly used in the northern part of the country—which is why it is usually associated with Hanoi-style pho, the more savory, stripped-down version of the noodle soup that is less common in the United States—she and her relatives have since noticed that it is increasingly available in the southern parts of Vietnam these days.

“Since I wrote about [sa sung] in 2011, it appears they have become more widespread,” Nguyen said. "I’ve seen them sold in boxes, very nicely packaged, at Cho Lon, the Chinese wholesale market in Saigon,” in the southern part of the country. Nguyen speculated that pho’s growing international cache, and a renewed interest in Vietnamese cuisine among successive generations of the Vietnamese diaspora, may be responsible for the fact that sa sung are more easily accessible.

But she also noted that sa sung are just one dried seafood product among many that are typically used in pho. “It turns out people add all kinds of seafood to their noodle soups. Some people add dried shrimp or squid,” Nguyen said. “The worms are a great umami source, and they’re great for when people don’t want to use MSG, but you can also use kombu. You’re just looking for glutamic acid, or glutamates.”

I asked Dennis Ngo, the chef at Di an Di, a Vietnamese restaurant in Brooklyn, about sa sung, and he essentially said the same thing. "[Using sa sung] is definitely something we considered as we were thinking about ways we could improve our stocks—any dried seafood component is helpful for adding umami—but we quickly realized it is extremely expensive and not realistic for a restaurant’s use,” Ngo said. But he added, "People swear by it, though, and they say it adds umami without adding too much seafood flavor.”

Taste-Testing Pho With and Without Sa Sung

Using the information I gleaned about the worms from my conversations with both Ngo and Nguyen, I conducted a series of informal taste tests at the office, pitting a batch of Kenji’s chicken pho broth against a batch of the same broth made with sa sung, and a third made with dried scallops, which Nguyen has suggested in the past offers a similar, if not identical, flavor profile to sa sung. All of them were seasoned with exactly the same amount of fish sauce, and I set them out for my colleagues to try. The results were mixed: Some preferred the broth with sa sung, others the plain broth; tasters liked the dried-scallop broth, but not as a pho broth, per se, which is also my heavily biased take on using dried scallops—I generally associate the taste of dried scallops in broth with wonton soup.

It was clear that the sa sung were adding a hint of sweetness and a broad savoriness to the soup, but it wasn’t necessarily true that we thought the sa sung broth was far and away the winner (although one taster was very, very enamored with the sa sung broth).

To get a better idea of how sa sung and dried scallops affected the broth, and how those broths would stack up against a broth made with MSG, Ngo graciously agreed to host a tasting using Di an Di’s house beef broth. Ngo had told me that their house broth is seasoned by a set, rather low ratio of MSG to broth. I asked that he prepare a house broth without MSG, one with MSG, and then a batch each of the no-MSG house broth simmered with dried scallops and sa sung.

This was not the most scientifically rigorous taste test; it was done just to get a sense of how these ingredients affected the broth, and I asked Ngo to use a rather large quantity of dried scallops and sa sung in order to get a clear idea of the resulting flavor profiles. Daniel joined me, as did Ngo’s business partner Kim Hoang, and we tasted each broth side by side, then tasted them all in a row, noting anything we found interesting about each one.

The main thing we all agreed on was Di an Di’s house broth, seasoned with MSG, was the favorite. The broth without MSG was a clear second. The two dried seafood broths, because of the large amount of dried seafood I had instructed Ngo to use, both had a striking marine aroma and flavor, throwing the broth out of balance and largely covering up its beefy base. Each was clearly identifiable, with the dried scallop–spiked broth having a fishy flavor and aroma, where the sa sung broth had a more unplaceable flavor that Daniel described as dried-fish with a very subtle aftertaste of bitterness. For my part, I found the sa sung broth to have a kind of muddy savoriness that I tasted in my nose, if that makes any sense. The scallop broth tasted to me like pho-ish wonton soup.

Is Sa Sung the Secret Ingredient for Great Pho?

The short answer is, “No.”

I think Nguyen has the best long answer, which is that sa sung has unique attributes, but understanding the role it plays in making pho broth is what’s important. "I don’t think [sa sung] are super pivotal. There are many other aspects of the broth that are pivotal, like good bones. [Sa sung] is an umami source. If you have a really good pho recipe, and you throw these worms in, then yeah, it will take it to the next level. But when I write recipes, I think about what happens when I don’t have this ingredient, because I’m trying to get Vietnamese food to be a part of people’s repertoire. I don’t want to make it exotic; I don’t want to make it fussy; I don’t want to make it precious in the sense that you have to run around and get a bunch of ingredients from a bunch of different markets. That makes the food inaccessible. As far as what I do as a writer and a cooking teacher, I need to make my cuisine understandable and accessible without dumbing it down. Sa sung is not like a silver bullet; there are so many other things in pho that make it excellent."

I called Phan, who, in addition to owning Sa Sung USA, the company importing and selling the worms, is executive chef of Hirotako, a San Francisco-based catering company, and he essentially confirmed much of what Nguyen and Ngo had said: he started importing the worms because of growing interest among friends and family about sa sung; it’s essentially a source for glutamates but has its own unique flavor. When I asked about the price point ($24.99 for 30g, not including shipping), he noted that they are, in effect, an artisanal product: All of the worms are harvested in the wild by hand, and he employs people in Vietnam to purchase directly from the harvesters. They then clean each worm—the process he described involves inserting a stick into the worm and turning it inside out to clean out sand—and air-dried on mesh screens, after which the dried product is shipped over en masse and packaged stateside.

Phan observed that some of the restaurants he supplies use sa sung as the main umami component, whereas others will use some sa sung and supplement their broth with a bit of MSG, which essentially confirms Ngo and Nguyen’s view on them: the worms are a pricey alternative to other umami sources.

For my part, since I eat a fair amount of pho at home, I find the worms to be incredibly appealing as an ingredient; the flavor that they impart is impossibly hard to describe, but it’s uniquely tasty, and one that I recognize (and, consequently, love) from that old bowl of pho I grew up eating. But if the price deters you, you can certainly look to other dried seafood products to use in your pho, or you can forgo them altogether.

How to Use Sa Sung in Pho Broth

Phan’s Sa Sung USA website has a recipe for beef pho that calls for using 10 grams of sa sung for an eight-quart pot of soup; in her pho cookbook, Nguyen recommends using anywhere from 15-25 grams for a similar quantity of broth. In my experience, keeping in mind the quality and expense of the worms Sa Sung USA sells, I’d be inclined more toward Phan’s recommendation, and since I used only about 5 grams in the first broth I made with the worms, I think that would also be sufficient to provide a nice umami roundness to the broth.

Nguyen notes in her book and online that sa sung’s sweetness should also be taken into account, so if the pho recipe you use has added sweetness, either in the form of rock sugar or, as Nguyen suggests, Fuji apple, you will want to omit the sweet element if using sa sung.

To prepare the sa sung, start by toasting them in a dry pan until they puff up and take on color. This step makes it easier to clean the worms, if they’re particularly sandy. Once inflated, you can break them open and tap out any sand that might be inside; if they are particularly sandy, you should cut them into pieces with scissors and rinse them. My experience with Phan’s worms, both the ones he sent as a free sample and a pouch I had a colleague order to their home, is that they are relatively sand free, and did not need rinsing.

I asked Phan about the difference between the larger worms and the smaller, more wrinkled ones (pictured above), and he said the older, larger worms are typically purchased as gifts in Vietnam, whereas the younger, smaller ones are typically purchased for home use. Sa Sung USA does not differentiate between the two and sells both varieties at the same price. There shouldn't be any difference in the quality of the flavor, but because the smaller worms are more difficult to clean than the larger ones, which sometimes necessitates breaking the worms' bodies up.

Phan emphasized the importance of the toasting step for another reason: flavor. Much like dried squid, the sa sung take on a smoky quality when lightly toasted, but can impart bitterness to the broth if they are over-toasted or burned.

After toasting and cleaning, put the sa sung into the pho pot along with the dried spices. Strain them out at the end along with all the other stuff in the pot, and you’ll have a deeply savory worm-spiked broth.