Healthy oven-baked Japanese candied sweet potatoes (daigaku-imo/大学芋)—fluffy when warm, silky when cool. No deep-frying, coated in a glossy sweet-savory glaze.
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🍁 From the Autumn Kitchen
When autumn arrives, sweet potatoes are always the first thing that comes to mind.
This year, I was lucky enough to find two beautiful varieties: the silky, honey-like Beni Haruka(紅はるか), and the rich, creamy Anno-imo(安納芋) with its vibrant orange flesh.
Most of them found their way into the oven as simple baked sweet potatoes(yaki-imo/焼き芋).
But with the rest, I wanted to create something special—these healthier oven-baked daigaku-imo (大学芋, Japanese candied sweet potatoes) made with less oil and sugar than the traditional deep-fried version.
What I love most is how the texture transforms: straight from the oven, they're gloriously fluffy and warm. But leave them overnight, and they become something entirely different—moist, tender, almost silky.
It's this play of textures that makes autumn cooking feel so generous, so full of possibility.
🧺 Recipe Features
- Easy & healthy daigaku-imo (大学芋) made in the oven without deep-frying
- Special sweet and savory glaze with less sugar to bring out the natural sweetness of the potatoes
- Perfect for an easy autumn vegan snack
🍠 Ingredients
Basic Ingredients
- Sweet Potatoes: I'm using Beni Haruka and Anno-imo this time. Both have that wonderful creamy, moist texture—and their colors are beautiful together. Smaller ones work best here.
- Glaze: Soy sauce, beet sugar, mirin, and vinegar brought together.
- Oil: Just a light coating on the surface before baking
- Black Sesame Seeds: Daigaku-imo needs black sesame—it adds that essential nutty aroma.
Optional
For when you want more depth:
- Salt: Just a pinch brings out the sweetness beautifully. Helpful when the flavor feels a bit flat.
- Coconut Oil: Adds a lovely richness at the end. Light-colored sesame oil (untoasted) or rice bran oil work well too.
See detailed measurements in the recipe card below 👇
🥄 Tools
- Knife and cutting board
- Pot
- Spoon and spatula
- Oven and baking sheet
- Parchment paper
- Paper towel
📖 Instructions
- Cut
- Wash the Japanese sweet potatoes and slice into rounds, about 1.5-2cm thick.
🌿 I'm using small sweet potatoes here, around 150g each. If yours are larger, aim for pieces about 1.5-2cm thick and 3-4cm across.
- Soak in Water
- As you cut, drop the pieces into water to keep them from browning.
- Let them sit for 5-10 minutes, then drain well.
🌿 If you're not worried about a bit of bitterness or discoloration—and can move quickly—you can skip this step. I find soaking gives a more tender, moist finish.
- Coat with Oil
- Pat the surfaces dry with paper towels.
- Line your baking sheet with parchment, drizzle the oil on it, and arrange the sweet potatoes while coating them by rolling in the oil.
- Bake
- Start at 200°C (no need to preheat) for 15 minutes.
- Then turn it up to 230°C and bake another 10-15 minutes until they're golden.
- Make the Glaze
- Combine all the glaze ingredients in a pot and bring to a boil.
- Once it's bubbling, lower the heat and simmer for about 1.5 minutes.
- Adjust the Flavor
- Let it cool a bit while tasting.
- Add salt or coconut oil if it needs it.
🌿 The glaze thickens as it cools—check the Kitchen Notes below for when to coat the sweet potatoes.
- Coat
- Add the baked sweet potatoes to the glaze in the pot, mixing gently to coat them all with the glaze.
- Sprinkle with black sesame.
- Spread on Baking Sheet
- Spread them out on the baking sheet so they don't stick together.
🌿 This step really helps keep them separate.
Eat them right away if you want that fluffy texture, or let them sit if you prefer them moist and tender.
📘 Kitchen Notes | Cooking Tips
➤ Glaze Thickness Guide
The glaze gets thicker as it cools. You want to add the sweet potatoes while it still flows smoothly from a spoon—before it gets too thick and clingy. That way everything gets coated evenly.
➤ Best Time to Eat
For that fluffy texture: Start making the glaze about 5 minutes before the sweet potatoes are done baking. Let it cool while they finish. Then coat them right away and eat while they're hot. (Watch out—they're seriously hot!)
For a moist, tender texture: They get softer and more luscious as they cool. Leave them overnight and they transform completely—the texture becomes silky and rich. It's like two different snacks.
📚 Notes | Q&A
The vinegar keeps the glaze from hardening too much—makes it so much easier to coat the sweet potatoes evenly. And don't worry about the sourness; it cooks off completely as it simmers. If you're unsure, I'd say try it with vinegar at least once and see what you think.
What I like to do: bake the sweet potatoes ahead of time, then make the glaze fresh right before eating. That way you get the best of both—the fluffy potato texture and that glossy, fresh glaze. Makes a big difference.
I'm using beet sugar here, but coconut sugar or light brown sugar work great too. White sugar is sweeter though, so you might want to use a bit less and taste as you go.
Add a bit more sugar to the glaze and taste as you go. The recipe is designed for naturally sweet varieties, so less sweet ones need a little help.
Eat them right out of the oven—that's the key. If you want extra fluffiness, starchier varieties like Naruto Kintoki (鳴門金時) or Beni Azuma (紅あずま) work great too.
🍽 Got Extra Sweet Potatoes?
Other ways I like to use them:
🎃 Kabocha Season
Some of my favorite autumn kabocha recipes:
✏️ Recipe Card | Summary
Oven-Baked Japanese Candied Sweet Potatoes
Equipment
- Knife and cutting board
- pot
- Spoon and spatula
- Oven and baking sheet
- parchment paper
- paper towel
Ingredients
Sweet Potatoes
- 600 g Japanese sweet potatoes (choose small ones, about 150g each)
- 1 tablespoon vegetable oil (rice bran oil, light sesame oil, etc.)
- Black sesame seeds (to taste)
Glaze
- 4 tablespoon mirin
- 2⅔ tablespoon sugar (see notes)
- 2 teaspoon soy sauce
- 1 teaspoon rice vinegar
Optional
- Coconut oil (or rice bran oil, light sesame oil to taste)
- Salt to taste
Instructions
- Cut: Wash sweet potatoes and cut into 1.5-2cm thick rounds.600 g Japanese sweet potatoes
- Soak: Soak cut pieces in water to prevent discoloration. Drain after 5-10 minutes.
- Dry: Pat surface moisture with paper towels.
- Oil: Line baking sheet with parchment, drizzle the oil on it, and arrange potatoes while coating them by rolling in the oil.1 tablespoon vegetable oil
- Bake: Bake at 200°C (no preheat) for 15 min, then at 230°C for 10-15 min until golden.
- Make Glaze: Boil glaze ingredients, reduce to low heat when bubbling, cook 1.5 min, remove from heat.4 tablespoon mirin2⅔ tablespoon sugar2 teaspoon soy sauce1 teaspoon rice vinegar
- Adjust: Taste while cooling, adjust with salt or coconut oil.Salt to tasteCoconut oil
- Coat: Add baked potatoes to the glaze in the pot, mix gently to coat them all, sprinkle with black sesame.Black sesame seeds
- Spread: Spread on baking sheet to prevent sticking.
- Serve: Eat immediately for fluffy texture, or wait for moist, tender texture.
Notes
☕️ Final Thoughts
This technique works beautifully with kabocha squash too, not just sweet potatoes.
For the squash version, I like to use maple syrup as the sweetener. Made in a toaster oven with just a touch of oil, it's both healthy and effortless—and that fluffy texture is what makes it truly special.
The perfect companion for those quiet autumn afternoons, watching the sun dip below the horizon.、
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