Summer weather in Korea isn’t just hot; it’s also incredibly humid, thanks to our summer monsoons. We like to cool down with ice-cold dishes, both sweet and savory. One of the easiest to make is oi naengguk (오이 냉국), a beloved cold cucumber soup. Back in our parents’ generation, before we had air-conditioning, it was an icy snacktime treat for people working under the sizzling sun out in the fields—they’d drink it down like water.
These days, recipes for oi naengguk have gotten sweeter and sweeter, but from what I remember, my grandmother added only Joseon ganjang (traditional soy sauce) to the thinly shredded cucumber and water. Simple and delicious.
A few tips for making oi ("cucumber") naengguk ("cold soup"): First, if you’re in the States and can’t get Korean cucumbers, try to use English cucumbers or other thin-skinned varieties. Avoid the fat, waxed cucumbers from the supermarket; their skin is too heavy and waxy, and they have an excess of seeds that don't work well in the soup. Use a mandoline for more evenly sized pieces of cucumber (if you're in the market for one, read Serious Eats' mandoline review).
When choosing a soy sauce, opt for Joseon ganjang, which is the more traditional Korean style made with soybeans only. It's sometimes also called "soup soy sauce," and it has a saltier, more savory, and more assertive flavor than the sweeter, Japanese-influenced yangjo ganjang, which also contains wheat. (Read more on Korean soy sauces and other pantry staples in our guide to essential Korean ingredients.)
If you can find it, try to use a cheongjang, or young, artisanal soy sauce with a lighter color. An older soy sauce will give you a much darker liquid base—in which case, you can use less soy sauce and more salt and ice, though you’ll miss out on some of that nice umami flavor.
The basic recipe for oi naengguk that I'm giving here (linked at the top and bottom of the page) contains very few ingredients: just cucumber, water (and ice), soy sauce, garlic, vinegar, salt, and roasted sesame seeds. There are lots of ways to change it up, though.
One common variation on oi naengguk uses miyeok, a seaweed often sold in the States under its Japanese name, wakame. For this option, soak 10 grams of dried miyeok in water for about 30 minutes.
Ten grams may not seem like much, but it is—when soaked, miyeok will increase about 10 times in weight and volume! That means you'll end up with about 100 grams of rehydrated miyeok, which will be more than enough to add to my base recipe. After soaking the miyeok, blanch, rinse, and squeeze it out before adding it to your soup.
You can also add thinly sliced and rinsed white onion and julienned carrot. And, while it’s not traditional, I think some julienned apple for a little extra sweetness is nice, too. If you’re adding apple, serve the soup right away, so the apple doesn’t sit around and turn brown.
Serve it in soup bowls, and don’t be afraid to pick up your bowl and drink it down—it’s a terrifically refreshing antidote to the sweltering summer weather.
(As told to Sonja Swanson.)