The first time I had sweet potato casserole was at Ruth’s Chris, and I understood the appeal immediately. Soft, rich sweet potato under a crunchy brown sugar topping. Half holiday side dish, half dessert.
I made it at home a few times after that before I started swapping in Korean sweet potatoes, and now I like it better this way. Korean sweet potato casserole has a denser, smoother filling, because goguma is drier than orange sweet potatoes and doesn’t go watery when you mash it. It’s also sweeter on its own, so the sugar in the recipe is doing less of the work.
Same buttery brown sugar crumble on top. Just a better base underneath.
Goguma has purple skin, but the inside is pale yellow. If you want a casserole that’s purple all the way through, try my purple sweet potato casserole instead.
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Jump to:
- Why This Recipe Works
- What Is Goguma (Korean Sweet Potato)?
- Ingredients
- Substitutions and Additions
- How to Make Korean Sweet Potato Casserole
- Make It Ahead
- Rose's Top Tips
- Variations
- What to Serve With This
- How to Store, Reheat, and Freeze
- Recipe FAQs
- More Sides for the Holiday Table
- Did you try this recipe?
- Korean Sweet Potato Casserole with Brown Sugar Walnut Topping
Why This Recipe Works
- The filling holds its shape. Goguma has less moisture to start with, so the mash stays thick after baking instead of loosening into something you serve with a spoon and a lot of hope.
- You control the sweetness. The potatoes are sweet enough on their own that you can cut the condensed milk by half if your table skews less sweet, and the casserole still tastes finished.
- It fits a holiday schedule. Assemble it the day before, keep the topping separate, and bake it the day of.
What Is Goguma (Korean Sweet Potato)?
Goguma is just the Korean word for sweet potato, and the ones sold under that name in Asian markets have purple skin with pale yellow flesh. They cook up drier and denser than the orange kind, with a flavor closer to roasted chestnut than to pumpkin.
That's the whole reason this casserole works. Less water in the potato means a mash that stays thick, and more natural sugar means the condensed milk isn't carrying the recipe by itself.
Ingredients
Here's what you'll need:
- Korean sweet potatoes, about 2 pounds, which is roughly 2 large ones. Peel and boil them before mashing.
- Condensed milk does most of the sweetening and adds body. Cut it by half if your table runs less sweet, and the casserole still tastes finished, since the potatoes bring their own sugar. Skip it entirely and the filling turns bland and loose, because you're removing sugar and thickness at the same time.
- Egg binds the filling and gives it a light, souffle-like set. Without it the casserole tastes fine but never firms up, so it slumps on the plate instead of holding a clean edge.
- Evaporated milk loosens the mash to a spreadable consistency. Goguma is dry, so you'll likely need every bit of it and possibly a splash more. Add it gradually rather than all at once.
- Cinnamon and nutmeg keep the filling from reading as straight dessert. Nutmeg does more than you'd expect here, so grate it fresh if you have a whole one.
- Salt is what makes the sweetness taste like flavor instead of just sugar. A casserole this sweet needs more than you'd think.
- Vanilla extract rounds the edges of the condensed milk, which can taste flat on its own.
- Butter, melted, goes into both the filling and the topping. In the filling it's richness. In the topping it's what turns the flour and sugar into crumbs instead of powder.
See recipe card for quantities.
For the Topping
- All-purpose flour gives the crumble structure so it holds together on top instead of dissolving into the filling.
- Brown sugar caramelizes as it bakes and gives the topping its color. Dark brown sugar makes it deeper and slightly molasses-y if that's what you want.
- Butter, melted. Too little and the topping stays sandy. Too much and it spreads into a single sheet instead of separate crumbs.
- Walnuts for crunch and a toasty flavor that stands up to the sweetness underneath. Pecans are the standard for this dish and work the same way. I used walnuts because that's what I had.
See recipe card for quantities.
Substitutions and Additions
- Regular orange sweet potatoes work, and the casserole will still be good, just different. They hold more water, so the filling comes out softer and closer to the classic version. Drain them well after boiling and hold back some of the evaporated milk until you see how loose the mash is.
- Frozen cubed sweet potato is fine if you thaw and drain it thoroughly. Canned is the one I'd skip here. It's packed in syrup and already soft, which fights everything the Korean sweet potato is doing for this recipe.
- Half and half or heavy cream in place of evaporated milk gives you a richer filling. Both are thinner than evaporated milk, so add them a little at a time.
- Pecans instead of walnuts is the standard for this dish and needs no other changes. For a nut-free topping, leave the nuts out entirely and add a couple tablespoons of rolled oats, which keeps some texture on top.
- Ginger or allspice if you want more spice. Both go further than cinnamon, so start with a quarter teaspoon.
- For a dairy-free version, use plant-based butter and an unsweetened dairy-free milk. Coconut milk works and does add a little coconut flavor, which suits this casserole more than it would the orange sweet potato version.
How to Make Korean Sweet Potato Casserole
- Prep the sweet potatoes. Peel and cut the Korean sweet potatoes into cubes of roughly the same size so they finish cooking at the same time. Boil in salted water until a fork slides through with no resistance, about 15 to 20 minutes. They're denser than orange sweet potatoes, so give them the full time if you're unsure. Drain well and mash while they're still hot, when they break down most easily.
- Make the casserole base. In a large bowl, stir the mashed sweet potatoes together with the condensed milk, egg, cinnamon, nutmeg, vanilla, and melted butter. Add the evaporated milk a little at a time until the mash is thick but spreadable, closer to soft mashed potatoes than to batter. Goguma is dry, so you'll probably use all of it.
- Prepare the topping. In a separate bowl, mix the flour, brown sugar, and melted butter until it clumps into crumbs. If it stays powdery, add melted butter a teaspoon at a time. Stir in the walnuts last so they stay in visible pieces.
- Assemble. Spread the sweet potato mixture into a greased casserole dish and smooth the top. Scatter the topping evenly over the surface rather than pressing it down, so it stays crumbly as it bakes.
- Bake. Preheat the oven to 350°F (175°C) and bake for 25 to 30 minutes, until the topping is golden and the filling is bubbling at the edges. The center should be set, not jiggly, when you nudge the dish.
- Serve. Let it rest for 10 to 15 minutes before serving. The filling firms up as it cools and slices much more cleanly than it will straight out of the oven.
Make It Ahead
You can assemble this casserole up to two days before you bake it. Mix the filling, spread it into the dish, cover it tightly, and refrigerate.
Keep the topping separate. Mix it, store it in a container at room temperature, and scatter it on right before the dish goes in the oven. If it sits on the filling overnight it draws moisture and bakes into a soft layer instead of crumbs, which is the whole reason people make the streusel version.
A cold casserole needs more time in the oven. Add about 10 to 15 minutes to the bake, and let the dish sit on the counter while the oven preheats so it isn't going in straight from the fridge. Check the same way you would otherwise: bubbling at the edges, set in the center.
Rose's Top Tips
- Use a food processor for a smoother filling. Hand-mashing leaves small lumps that stay in the finished casserole, since nothing in the bake breaks them down further. A few pulses in the processor gets you an even texture, but stop there. Goguma is starchy enough that over-processing turns it gluey.
- Salt more than feels right. With condensed milk, brown sugar, and naturally sweet potatoes all in one dish, salt is the only thing keeping it from tasting flat.
- Cut the condensed milk by half for a less sweet casserole. The potatoes carry enough sugar on their own that the filling still tastes finished, and the topping keeps its full sweetness either way. Worth doing if this is going on a table alongside ham or anything else glazed.
Variations
- Marshmallow topping. Skip the crumble and use mini marshmallows instead. Bake the casserole on its own for 20 minutes first, then scatter the marshmallows over the top and return it to the oven for 5 to 10 minutes, until they puff and brown. Added at the start they burn before the filling is done.
- Half and half. Crumble on one side of the dish, marshmallows on the other. Bake with the crumble for 20 minutes, add marshmallows to the empty half, then finish. Useful when the table is split on this, and it usually is.
- Pecans instead of walnuts. Pecans are the standard for this dish and work exactly the same way. I used walnuts because that's what I had in the pantry, and I've kept making it that way since.
- Coconut sugar in place of brown sugar. Less sweet with a slightly caramel edge. It browns faster, so check the topping a few minutes early. Swapping coconut oil for the butter works too, though the topping comes out sandier and less rich.
What to Serve With This
- Glazed ham. The pairing I'd reach for first. An orange maple glazed ham gives you the sweet and salty contrast that keeps this casserole reading as a side instead of a second dessert.
- Roast chicken or turkey. Same job, milder. Good if the rest of the table is already sweet.
- Something sharp or green. Green beans, a salad with vinegar in the dressing, or cranberry sauce. This is a sweet dish, so it needs something acidic next to it more than most sides do.
- The soft, rich sides. Mashed potatoes, dinner rolls, mac and cheese. All fit the table, just don't build a plate entirely out of them or it gets heavy fast.
- On a full holiday spread, this earns its spot next to the stuffing rather than near the pie.
How to Store, Reheat, and Freeze
Leftovers keep in an airtight container in the fridge for up to 4 days. The topping softens after the first day, which is unavoidable once it sits against the filling.
To reheat, cover the dish with foil and warm it at 350°F until heated through, about 20 minutes for a full dish or 10 for a smaller portion. Pull the foil off for the last few minutes to bring some crispness back to the topping. The microwave works for a single serving and takes about a minute, though the topping goes soft.
You can freeze it baked or unbaked, for up to 2 months either way. Unbaked freezes better: assemble the filling in the dish without the topping, wrap it tightly, and freeze. Thaw overnight in the fridge, add the topping, and bake as directed with about 10 extra minutes. If you're freezing it already baked, thaw it the same way and reheat covered.
Recipe FAQs
H Mart, 99 Ranch, and most Asian grocery stores carry them year round. Trader Joe's and Whole Foods usually stock the same thing labeled Japanese sweet potato or murasaki, and either works here.
Yes. The filling comes out softer and closer to the classic version, since orange sweet potatoes hold more water. Drain them well and hold back some of the evaporated milk until you see how loose the mash is.
Usually too much liquid added at once, or potatoes that weren't drained properly after boiling. Add the evaporated milk gradually and stop when the mash is thick but spreadable. Going the other way, if the mash is too stiff to spread, add more evaporated milk a splash at a time.
Korean sweet potatoes have purple skin and pale yellow flesh. They're drier, denser, and sweeter than orange-fleshed sweet potatoes, with a flavor closer to roasted chestnut.
Yes for this recipe. The skin is edible, but it turns leathery in a baked casserole and shows up as dark flecks in the filling.
Yes, baked or unbaked, for up to 2 months. Unbaked gives you a better result. See the storage section above for the full method.
More Sides for the Holiday Table
If you don't think this sweet potato casserole is a dessert, here's more option:
- Candied maple walnuts. Make a batch and use them on top of this casserole instead of the plain walnuts in the crumble. They also cover the snacking bowl nobody remembers to fill.
- Crack green beans. The salty, savory counterweight this casserole needs sitting next to it.
- Sausage green bean potato casserole. A fully savory casserole for the same table, and it bakes at the same temperature, so the two can share the oven.
- Air fryer sweet potato wedges. For the leftover sweet potatoes, or for when you want the ingredient without the whole production.
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Korean Sweet Potato Casserole with Brown Sugar Walnut Topping
Equipment
- 1 Pie baking plate
Ingredients
- 2 large Korean Sweet Potatoes
- ½ cup Condensed Milk
- 1 Egg
- ½ cup Evaporated milk
- ½ teaspoon Cinnamon
- ¼ teaspoon Nutmeg
- ½ teaspoon Salt
- 2 teaspoon Vanilla Extract
- ½ cup Butter melted
Topping Ingredients:
- ⅓ cup All-Purpose Flour
- ⅓ cup Dark Brown Sugar
- 3 tablespoon Butter cold
- 1 cup Walnuts chopped
Instructions
- Prep the Sweet Potatoes: Peel and chop the Korean sweet potatoes into cubes. Boil in salted water until tender, about 15-20 minutes. Drain and mash until smooth.
- Make the Casserole Base: In a large bowl, mix the mashed sweet potatoes, condensed milk, egg, milk, cinnamon, nutmeg, salt, vanilla extract, and melted butter. Stir until everything is combined.2 large Korean Sweet Potatoes, ½ cup Condensed Milk, 1 Egg, ½ cup Evaporated milk, ½ teaspoon Cinnamon, ¼ teaspoon Nutmeg, 2 teaspoon Vanilla Extract, 3 tablespoon Butter, ½ teaspoon Salt
- Prepare the Topping: In a separate bowl, mix together the flour, brown sugar, and melted butter until it forms a crumbly mixture. Stir in the walnuts.⅓ cup All-Purpose Flour, ⅓ cup Dark Brown Sugar, ½ cup Butter
- Assemble the Casserole: Spread the sweet potato mixture into a greased casserole dish. Evenly sprinkle the walnut topping over the top.1 cup Walnuts
- Bake: Preheat your oven to 350°F (175°C). Bake the casserole for 25-30 minutes, until the top is golden and bubbly.
- Serve: Let it cool slightly before serving, and enjoy the creamy, crunchy deliciousness!
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