Kongguksu — The Cold Noodle That Splits Korea Into Salt and Sugar

Last year, the K-pop group ILLIT slipped kongguksu into a song — calling it a limited-edition summer thing, and claiming it's nuttier than matcha. Both parts happen to be true, which is what makes the line land.

Kongguksu is Korea's cold soybean noodle soup, and it really is limited. The broth is served chilled, so the dish arrives with the heat and vanishes when the weather turns — everywhere for a few months, then gone for the rest of the year. As for the nuttiness: the broth is nothing but ground soybeans and water, yet served cold and silky it turns deeply toasty and rich, rounder than soy milk and, yes, nuttier than matcha. On a day too hot to want much of anything, few bowls are this satisfying. If a single dish could stand in for a Korean summer, kongguksu would be a strong contender.

A Simple Bowl with a Short History

For all that, kongguksu is about as plain as a dish gets: cold soybean broth poured over noodles, finished with a little cucumber and sesame. No stock to simmer, no fermented paste, no cooking at all once the broth is made. Beans, water, noodles, ice.

It feels like something Koreans must have eaten forever, and the soybean itself nearly is. It was long the protein of ordinary people — the food you could count on when the finer grains went to the wealthy. The 18th-century scholar Yi Ik put it plainly in his writings: the best dishes went to the privileged, he observed, while it was the humble soybean that kept the poor alive — and ground down and boiled into a soup, it made something genuinely good to eat. In his day, that grinding was done on a matdol, a stone mill of two heavy discs that crushed soaked beans into a coarse paste by hand — the ancestor of today's blender, which makes the same broth a five-minute job.

The cold noodle dish itself, though, came much later. Naengmyeon, the cold buckwheat noodles that share the summer table, appears in Korean writing as early as the 1600s; kongguksu shows up only near the end of the 1800s. Its first clear recipe is in a cookbook called Siuijeonseo — soak the beans, blanch them lightly, pass them through a fine sieve, season with salt, and pour the broth over wheat noodles. That's very nearly the bowl Koreans still make today, and yet it's generally thought to be only about a century old: strikingly young for a dish that feels so timeless.

What made it a true summer staple came later still. In the 1960s and 70s, the government urged people to eat wheat and mixed grains in place of rice, and cheap wheat noodles paired naturally with inexpensive, protein-rich soybeans. The result was filling, cooling, and nourishing in exactly the season that wears a body down — and that is when kongguksu settled into the role it still plays: a humble restorative for the depth of summer.

A Summer Lunch, and an Easy One to Make

You'll most often meet it at lunch, on the kind of day when the heat makes a hot meal unthinkable. Noodle houses and casual diners put it on the menu only for the season, and you'll even find it at Chinese-Korean restaurants as a summer special. Buddhist temples have long served it too, as a cooling way to work protein into a meatless summer table.

But for all its presence in restaurants, kongguksu is, at its core, home food — and an unusually forgiving one to make. There's no broth to babysit and no technique to master, just beans to soak ahead of time and noodles to boil at the end. If you can run a blender, you can make it. So it's worth doing once yourself, in your own kitchen, where the whole thing comes down to getting one element right.

Making Kongguksu at Home

That element is the broth. Everything else is just assembly.

The broth. Start with dried yellow soybeans — the pale variety called baektae. Rinse them and soak them in cold water until they soften, ideally overnight. Boil them in fresh water until just tender, around fifteen minutes; the trick is to stop there, since overcooking is what turns the broth beany rather than clean. Drain, rinse under cold water, and rub off any loose skins. Blend the beans with cold water until completely smooth — strain it for a lighter broth, or leave it as is for something heartier — and chill it well.

The noodles. Thin wheat somyeon is the classic choice. It cooks in a couple of minutes and stays light enough to let the broth lead. Boil it, rinse under cold water until the strands are cool and springy, and drain.

Putting it together. Settle the noodles into a wide bowl and pour the cold broth around them until they're half-submerged. Top with fine matchsticks of cucumber, a scatter of toasted sesame, and a few cubes of ice to keep it cold to the last bite. That's the bowl in its plainest form — and from there, it's easy to take in a different direction.

Nuttier, or Lighter

For something richer, lean further into the nuttiness: blend a spoonful of toasted sesame or a few pine nuts into the broth, or add toasted peanuts for a creamier, rounder result. Black soybeans in place of yellow give a darker, earthier bowl that's almost a different dish. And beyond the cucumber, sliced tomato is a common summer touch, while a boiled egg or a tangle of young radish kimchi turns the bowl into a fuller meal.

For something lighter, gluten-free rice somyeon steps in for the wheat noodles, prepared in exactly the same way, leaving the soybean broth to lead.

However you build the bowl, though, one decision always waits until the very end — and it's the one Koreans can't agree on.

Salt or Sugar?

Kongguksu isn't seasoned in the pot. You add it yourself at the table, and what you reach for tends to depend on where you grew up.

In the southeast, around the Gyeongsang region, the answer is salt — a pinch that turns the broth savory and pushes the soybean forward. In the southwest, in Jeolla, many reach for sugar instead, coaxing the broth into something gently sweet. Neither side gives much ground. There's a well-worn joke that the two regions could reconcile every other rivalry between them and still come to blows over a single bowl of cold soybean noodles. For a newcomer, the happy truth is that there's no wrong answer here — only a fork in the road, and the easiest way to find your side is to try both at least once.

The broth itself divides people too, though along different lines. Made from nothing but beans and water, it carries a faint raw-bean taste that some find comforting and others can't get past. Cooking the beans just right, rinsing away the skins, and serving everything very cold all soften that edge — but kongguksu is, honestly, a bowl you tend to either crave or quietly skip. Most people who grew up with it land firmly in the first camp.

Kongguksu asks almost nothing of you — a handful of beans, some noodles, and an afternoon hot enough to call for it. It comes with the heat, stays only as long as summer does, and tastes far better than something this plain has any right to. Make it once this season, cold and nutty, and let yourself land on a side. Salt, or sugar. Everyone ends up somewhere.

FAQ

Can I make the broth ahead of time?
Yes. It keeps covered in the fridge for a day or two. It settles as it sits, so stir or shake it before serving. Cook the noodles fresh just before eating — they don't hold up once they've soaked.

Do I have to use somyeon, or will other noodles work?
Somyeon is the most common, but kongguksu is flexible. Thicker kalguksu-style wheat noodles work well, and some shops use Chinese-style noodles. Just rinse whatever you use under cold water so it stays firm in the chilled broth.

Is kongguksu vegan?
The basic bowl is — just soybeans, water, and noodles. Keep an eye on the toppings if it matters to you: egg is common, and some kimchi is made with fish sauce.

Are the toppings fixed?
Not at all. A little cucumber is the usual touch — cool and crisp against the broth — but you can leave the bowl bare, or add other light summer produce: sliced tomato, fresh sprouts, a halved boiled egg. The only rule is to keep it on the lighter side, so nothing competes with the soybean.

What do Koreans eat alongside it?
Not much, by design. A small dish of kimchi or some danmuji, the yellow pickled radish, is typical. It's meant to be a light, self-contained meal for a hot day.