Thanksgiving dinner has an oven problem. The turkey owns it for hours, the rolls wait their turn, and every side dish that wants a hot oven is quietly bargaining for the rack.
Goguma mattang (고구마 맛탕) skips the line. It is Korean candied sweet potato, made entirely on the stovetop: chunks of sweet potato are fried, then tossed in a caramel that hardens into a glassy, crunchy shell.
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| Goguma mattang is fried sweet potato coated in a caramel that hardens into a crunchy shell. |
Sweet potatoes already belong on the holiday table. Smithsonian Magazine notes that they were likely served at Thanksgiving meals in the 1800s because they keep well, and that candied versions became common by the late 1800s. Mattang is a crunchier relative of that idea.
It is also a dish that fails in a very specific way. The sugar either turns into a smooth, glossy coat or seizes into a lump, and most of that is decided before the potatoes ever go in the pan. So the failure points come first below, and the recipe card comes after.
What Goguma Mattang Is
Goguma mattang is deep-fried sweet potato coated in caramelized sugar syrup that sets into a hard shell. Hyegyoung K. Ford of Beyond Kimchee explains that mattang (맛탕) names the technique of glazing deep-fried ingredients in caramelized syrup, and that the technique is applied to other ingredients too, which is why the sweet potato version is called goguma mattang.
She says it has been popular for generations and was a street food she ate growing up. She also notes that it resembles the Japanese dish daigaku imo, but that the Korean version has a crunchier, almost brittle shell.
Daigaku imo, according to Tasting Table, means "university potato" and began appearing in the early 20th century around Tokyo college campuses, with a glaze of sugar, soy sauce, mirin, rice vinegar and water. None of the sources reviewed here settles where mattang itself came from, so the Japan connection is best treated as a resemblance and not a documented lineage.
For a North American comparison, the shell is closer to toffee or peanut brittle than to the soft, syrupy sweet potatoes many holiday tables already have. That is the whole reason to make it. It adds a crunch to a plate that is mostly soft.
Where Mattang Goes Wrong
Most ruined batches trace back to the sugar, and the sugar fails in a handful of predictable ways. The good news is that four separate recipes, three in English and one Korean news piece, agree on almost every fix.
Stirring the Melting Sugar
The most repeated warning is not to stir sugar while it melts. Maangchi puts it directly: keep moving the pan, because stirring makes the sugar crystallize. Irene Yoo at The Kitchn sprinkles the sugar in a thin, even layer, heats it undisturbed for 4 to 5 minutes, then swirls the pan by its handle and says plainly not to stir.
Beyond Kimchee scatters the sugar over a tablespoon of oil and lets it melt without stirring, then gently shakes or swirls the pan. A Korean news article from WikiTree (September 30, 2026) says the same: let the sugar melt undisturbed rather than stirring constantly.
Timing the Syrup
Caramel moves quickly from golden to bitter. Beyond Kimchee warns that it darkens fast and turns bitter if overcooked, and Maangchi says to keep the heat low and watch it. The WikiTree piece adds that syrup hardens as it cools, so there is no point boiling it for long.
Syrup timing is also where the sources differ slightly. Maangchi cooks the sugar to a brownish syrup, then adds the potatoes. WikiTree suggests turning off the heat first and adding the potatoes once the syrup is thick but still loose. If your coating will not harden, Maangchi's fix is simply to cook the syrup a little longer next time, and she reminds readers that stove heat varies.
Corn syrup is the optional insurance. Beyond Kimchee adds 1½ tablespoons, near the end, once most of the sugar has caramelized, and says it slows hardening while still giving a hard, crunchy shell. WikiTree adds corn syrup or oligosaccharide (올리고당) earlier, once small bubbles form and the sugar starts to color. Pick one approach and keep it consistent between batches.
Coating and Spacing the Pieces
Once the potatoes hit the syrup, the risk shifts from the sugar to the pieces fusing together. The Kitchn warns that overstirring can make the potatoes stick to each other and advises a gentle, quick touch with as little stirring as possible. Parchment helps, since it keeps the pieces from sticking to each other or to the plate.
Maangchi says to coat the potatoes while the syrup is hot so the coating goes on evenly, then spread the pieces on parchment with gaps between them. Beyond Kimchee and WikiTree both say to spread them apart so they do not touch while the shell sets. If you want sesame seeds, add them right after coating and before the shell hardens.
Frying the Potatoes Properly
The coating can only be as crisp as the potato underneath. Beyond Kimchee dries the potatoes well before frying and fries in batches so the pan is not crowded, with the oil at 350°F (175°C). Maangchi fries at about 340°F for 4 to 5 minutes until light golden, and her diagnosis is simple: if the pieces come out floppy, fry them longer.
There is a shortcut for people without a deep-frying setup. The WikiTree article microwaves bite-size pieces for about 3 to 4 minutes, only until a chopstick slides in, then pan-fries them in 2 to 3 tablespoons of oil over medium heat. It warns that overcooked pieces can break when flipped. This is one Korean news outlet's method, and no comparison against the traditional fry turned up.
Mattang on a Thanksgiving Table
Mattang suits a holiday because it asks nothing from the oven and holds up for hours. Maangchi says it can be made 5 to 7 hours ahead and kept at room temperature, which fits the awkward window between starting the sides and carving the bird.
The Kitchn serves it immediately or at room temperature, and the author also likes it cold or with ice cream, so it can wander into dessert territory. Leftovers keep in the fridge for up to 3 days, and Yoo says they can be reheated though she prefers them cold. Beyond Kimchee is blunt about what time does: the shell softens into a sweet syrup and loses its crunch, though it stays tasty.
The sources give recipes for a single pound of sweet potatoes, serving about 3 to 4 people according to Maangchi. For a larger group, the safest approach is probably several small batches and not one giant one, since a big pan of caramel is harder to control. That is a suggestion rather than a tested rule.
On the sweet potato itself, the recipes call for Korean-type varieties: Maangchi says Korean sweet potato, The Kitchn calls for white-fleshed Asian sweet potatoes, and Beyond Kimchee says Korean or Japanese ones with purple skin and yellow or white flesh. Orange-fleshed American sweet potatoes are not covered by any of them, so expect the texture to differ.
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| Coat the fried pieces while the syrup is hot, then spread them apart on parchment to set. |
The Recipe Card
This version follows Maangchi's recipe (posted December 2010, updated May 2022), with notes from the other sources, and it has not been tested here. Both the oil and the caramel are extremely hot, so handle them carefully.
Ingredients (Quick Guide)
You need 1 pound (450 g) of Korean sweet potato, about 1/3 cup of white sugar, neutral cooking oil for frying (about 1½ inches deep) plus 2 tablespoons for the syrup, and 1 teaspoon of toasted black sesame seeds if you want them. Plan on 3 to 4 servings.
Step 1: Cut and Dry
Peel and wash the sweet potato, then roll-cut it into ½ to 1 inch pieces. Dry the pieces thoroughly, as Beyond Kimchee advises, before they go into the oil.
Step 2: First Fry
Heat the oil to about 340°F and fry the pieces for 4 to 5 minutes, stirring occasionally, until light golden brown. Drain them. If you are working in batches, do not crowd the pan.
Step 3: Make the Syrup
Swirl about 2 tablespoons of oil in a skillet, then sprinkle the sugar over it in a thin, even layer. Heat over medium until the sugar starts melting, about 5 minutes, then lower the heat to medium-low. Lift and move the pan so the sugar melts evenly, without stirring, for another 2 to 3 minutes until it becomes a brownish syrup, then turn off the heat.
Step 4: Second Fry (Optional)
Maangchi reheats the oil to 340°F and fries the potatoes a second time for 1 to 2 minutes until crunchy and golden, then drains them. The Kitchn skips the second fry, so treat this step as a way to push the crunch further.
Step 5: Coat
Reheat the syrup, add the potatoes, and mix with a wooden spoon until fully coated. Sprinkle on the sesame seeds right away, before the shell starts to set.
Step 6: Cool Apart
Transfer the pieces to a parchment-lined baking sheet with gaps between them. Leave them until the syrup hardens, then move them to a serving bowl. If the coating stays tacky, the syrup needed more time. If the potatoes feel soft, they needed more time in the oil.
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| Mattang adds a crisp, shiny bite to a table of mostly soft holiday sides. |
Because the sugar is the unforgiving part, a trial run a week before the holiday is cheap insurance. Make a half pound, watch how your stove behaves, and write down the timing that gave you a clear, hard shell. Then the real batch on Thanksgiving, which falls on November 26 this year, is just a repeat.
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