The smoke reaches you before you see the fire. It drifts across the corner in a thin gray ribbon, and inside it is something that smells like burnt sugar and wood at once, coming from a squat metal drum on a cart, a chimney pipe out the top and a slow fire inside. The vendor lifts a lid, turns a row of blackened sweet potatoes with long tongs, and closes it again, and for a second the whole corner smells like the inside of the drum. Nobody walking past that smell keeps walking at the same speed.
Gun-goguma is Korean roasted sweet potato, cooked whole over a wood fire until the skin blisters and the sugars inside run. Korean sweet potatoes usually have reddish-purple skin and pale, dense flesh, closer to a roasted chestnut than to the orange "yams" of an American Thanksgiving, which are sweet potatoes too. In winter they share the street with roasted chestnuts and, behind fogged glass, steamed buns.
After the paper bag and the paper cup, this is the last of the winter street's warmth, and it is the slowest. It arrives wrapped — in a skin, a shell, a cloud of steam — and you have to peel it, crack it, or blow on it before you can eat it. That small delay is the whole pleasure, and it starts at the drum.
Korean Sweet Potato, Up Close
The drum is the thing to look for. A steel barrel cut open and fitted with a door, set on a cart, fed with firewood, its pipe leaking smoke into the cold, vendors have roasted sweet potatoes in converted drums like this since around the Korean War, by Korea JoongAng Daily's account. There are fewer of them now than there once were. But when one sets up on a corner, it changes the whole block's weather.
Watch one for a while and you see how much judgment goes into it. The vendor keeps the potatoes moving, the biggest ones deepest in the heat and the finished ones resting near the door, where they stay warm without burning, and checks each with a squeeze of the tongs the way a baker taps a loaf. When you buy, you point, and the vendor picks the one that is ready, which is not always the one you pointed at. That is a kindness, and you should accept it.
Roasted chestnuts, gun-bam, are the drum's twin on the same corners. They are scored before roasting so the shell splits instead of bursting, then sold by the paper bag from late autumn through winter, and on the coldest nights it is hard to say which of the two smells is reaching you first.
The sweet potato inside the drum is a newer arrival than most Korean staples. Its seeds reached Korea in the 1760s, when the envoy Jo Eom obtained them on Tsushima during a mission to Japan, by the Encyclopedia of Korean Culture's account. It took root as a hedge against hunger, and it became a winter food for a practical reason. Stored through the cold months, sweet potatoes turn sweeter as their starch slowly becomes sugar.
My mother loves sweet potatoes more than anyone I know. Every autumn at harvest she drives out to Ganghwa Island, west of Seoul, where farms sell them by the box, and comes home with one, sometimes two, to keep in a cool corner. She eats from it all winter, from the week she brings it home until the box is empty, and the potatoes seem to get a little sweeter every time she reaches in.
For years, the home version was a pot of them steamed, set on the table with a bowl of dongchimi, radish water kimchi, so cold it still had slivers of ice in it, the way many Korean households paired them on long, dark evenings, sweet and starchy against cold and sour. These days, at my mother's, the air fryer does the job instead, and the potatoes come out blistered and sticky at the ends, as close to the drum as a kitchen gets. I still eat the first piece plain, before the dongchimi touches it, to taste what the winter has done to it. There is no recipe for any of it. Just the box, the basket, and the cold.
Koreans sort them by texture rather than color. Bam-goguma, chestnut sweet potato — the name is fair — is dry and crumbly when roasted, nutty and dense, and sticks pleasantly to the roof of your mouth. The softer, moister kinds, including hobak-goguma, pumpkin sweet potato, whose flesh runs orange, turn almost custardy in the heat, sweet enough to taste of honey. People choose by how they want the evening to feel, and most households keep a clear favorite.
For an American reader, the nearest memory is probably a Thanksgiving casserole, orange and buttered, sometimes under a lid of marshmallows. The Korean winter sweet potato is almost the opposite: eaten plain, out of its own skin, with nothing added, as a snack rather than a side. Its sweetness is the point, and nobody thinks to improve on it. The cold and the drum have already done that.
The other wrapped warmth of winter comes in steam. Hoppang began as a brand name in the early 1970s and became the everyday word for a steamed bun; the name plays on the sound you make blowing on something too hot to bite. For decades, a glass steamer by a shop counter, buns stacked inside behind fogged glass, was how you knew winter had started. Some convenience stores still keep one, but these days most hoppang go home by the bagful and into the microwave, and the flavors multiply every winter: red bean first, then vegetable, pizza, and stranger things each year.
I keep a bag in the freezer from November on, microwave them one at a time, and will defend the pizza one to anyone; the vegetable one is a close second. But I still buy the first hoppang of the year from a shop steamer on purpose. Peeling the thin square of paper off its bottom, slowly, so none of the bun comes away with it, standing outside with the steam on my face, is the closest thing winter has to a starting gun.
Its older cousin, jjinppang, is a steamed wheat bun filled with sweet red bean paste, its dough traditionally leavened with makgeolli, the cloudy rice brew, for a faint, pleasant sourness. In Anheung, a small town in Gangwon Province, travelers crossing toward the east coast once stopped to buy them and carried them, still warm and wrapped, for the road.
Sweet potato, chestnut, bun: none of them asks for a kitchen of equipment. An oven and a steamer basket will bring most of the corner indoors. But first, eat one the way the street does, standing up, with your gloves off.
The First Taste
The vendor picks one out with the tongs and hands it over, and it is hotter than anything you have held all day. You juggle it from palm to palm. Your fingers sting, then relax.
Break it in half. The steam comes up gold, and the smell is sweeter than it was from the street. Peel it with your fingertips, one strip at a time, and eat the flesh closest to the skin first, where the sugars leaked out and turned dark and sticky, almost candied. If it is a bam-goguma, the inside crumbles like a roasted chestnut; if it is one of the soft ones, it is close to spoonable.
The chestnuts come in a small paper bag. Press one between thumb and finger where the score has opened, and the shell gives with a dry crack. The nut inside is warm and floury, sweeter than you expect, with a faint smoky edge from the drum. Eat three before you realize you have eaten three.
On the way home, buy one hoppang from the steamer, if you can find one. The skin is soft and faintly sweet, and the red bean inside is hot enough to burn. Blow on it first. That is what its name is telling you to do.
Twenty minutes later, your hands are sticky and smell faintly of smoke, and there is a small heap of skins and shells in the bottom of the bag. You worked for every bite. The cold never stood a chance.
In Your Kitchen
The sweet potato is the easiest of the three to bring home, and the most forgiving. Look for Korean or Japanese varieties at an Asian market, with reddish skin and pale flesh, and keep them somewhere cool and dark rather than the refrigerator, which ruins their texture. A week on the counter, out of the sun, makes them noticeably sweeter, the same slow change the cold months bring.
- Roast. Scrub the potatoes and dry them well. Roast them whole on a rack at 400°F for 50 to 60 minutes, turning once, until the skin wrinkles and dark syrup begins to bead at the ends. Nothing else goes on them; that is all gun-goguma is.
- Rest. Leave them in the turned-off oven for 10 minutes more. The sugars keep caramelizing, and the flesh near the skin turns dark and sticky.
- Or steam. For the home version, steam them whole for 30 to 40 minutes, until a chopstick slides through, and serve with a bowl of cold dongchimi or a few strips of well-aged kimchi.
In most Korean homes now, the air fryer has taken over from the oven: 400°F for about 40 minutes, turned once, and the skins blister like the drum's. For chestnuts without scoring, roasting, and burnt fingers, Gongju's peeled, ready-roasted → chestnuts taste close to the paper bag. And for the steamed buns, look in the freezer case of a Korean grocery and do what most Koreans now do: sprinkle one with a little water, cover it, and microwave it for about a minute, or steam it from frozen for 12 to 15 minutes for a softer skin.
If a roasted sweet potato is left over, do what Korean cafés do every fall and winter. Blend it with a cup of warm milk, a pinch of salt, and a spoonful of honey into goguma latte, or keep a jar of → sweet potato latte powder for nights when the oven stays off. Drying sweet potatoes is an old habit in parts of Korea, too, and today's chewy → half-dried sweet potato from Haenam, at the country's southwestern tip, is the version that lives happily in a pantry. Roasted potatoes keep three days in the refrigerator and reheat in a dry pan or air fryer in about 5 minutes.
Warmth You Have to Work For
Most comfort food asks nothing of you. The last of the Korean winter street asks a little: a skin to peel, a shell to crack, a bun to blow on before the first bite. That small work is what makes it feel earned, a warmth you unwrap with your own cold hands on the darkest evenings of the year. It is also why it tastes best eaten slowly, standing up, in the company of whoever else stopped at the drum. Roast one this winter, peel it standing at your kitchen counter, and eat the part nearest the skin first.
FAQ
What is a Korean sweet potato? A Korean sweet potato, goguma, is a sweet potato with reddish-purple skin and pale yellow, dense flesh, nuttier and drier than the orange sweet potatoes common in American supermarkets. Koreans sort them by texture: bam-goguma is dry and crumbly like a roasted chestnut, while softer kinds such as hobak-goguma are moist and very sweet. In winter they are roasted whole in street drums. In the United States, look for them at Asian markets labeled Korean or Japanese sweet potatoes.
Is a Korean sweet potato the same as a yam? A Korean sweet potato is not a yam; it is a sweet potato, as are the orange "yams" sold in American supermarkets. True yams are a different plant, starchy and rarely sweet, and in the U.S. the USDA requires produce labeled "yam" to carry the words "sweet potato" as well. The Korean kind differs from the American orange one in color and texture, not in species family. It roasts drier, nuttier, and closer to a chestnut.
How do I roast Korean sweet potatoes at home? Korean sweet potatoes roast best whole, at 400°F for 50 to 60 minutes on a rack, turned once, until the skin wrinkles and syrup beads at the ends. Leaving them in the turned-off oven for 10 minutes more deepens the caramelized layer under the skin. Many Korean households now use an air fryer instead, at the same temperature for about 40 minutes. No foil is needed; the skin protects the flesh.
What is hoppang? Hoppang is a Korean steamed bun, most often filled with sweet red bean paste, sold warm through the cold months. The name began as a brand name in the early 1970s and became the everyday word for this kind of bun; it plays on the sound of blowing on something hot. Vegetable, pizza, and new flavors every winter came later. Most Koreans now buy them by the bag and microwave them at home, about a minute with a sprinkle of water; steaming from frozen takes 12 to 15 minutes.
How do I store Korean sweet potatoes, and how long do they keep? Raw Korean sweet potatoes keep for several weeks in a cool, dark, dry place with good airflow, but should not go in the refrigerator, which hardens the center and dulls the flavor. A week of resting at room temperature makes them sweeter as their starch turns to sugar. Once roasted, they keep about three days in the refrigerator. Reheat in a dry pan, oven, or air fryer rather than the microwave to keep the skin from going soggy.
When are roasted sweet potatoes in season in Korea? Roasted sweet potatoes are a late-autumn and winter food in Korea, roughly November through February. Sweet potatoes are harvested in autumn and grow sweeter in storage, so the ones on the street in midwinter are often the best of the year. Roasted chestnuts and steamed buns appear in the same weeks. The drums tend to disappear with the first warm days of spring.