With crispy skin and buttery tender bites, these Japanese Candied Sweet Potatoes (Daigaku Imo) is a classic Japanese snack to enjoy in fall and winter. They are glazed in a caramelized syrup for just the right amount of sweetness. So good with a cup of green tea!
Growing up in Japan, I was always more partial to traditional Japanese snacks over western-style sweets like cakes and cookies that most Japanese children enjoy. One of my absolute favorites is Candied Sweet Potatoes, or we call them Daigaku Imo (大学芋).
When I was in kindergarten, I remember I went to harvest Japanese sweet potatoes as part of the school excursion. All the kids brought home fresh sweet potatoes straight from the field, and my mom turned them into these bright, candied sweet potatoes. My dad and I are big sweet potato fans so we gobbled them up quickly.
What is Daigaku Imo (University Potato)?
These candied sweet potatoes are called Daigaku Imo in Japanese, and they are a sweet snack made of deep-fried Japanese sweet potatoes that are covered in a hard sugar candy coating.
You may wonder why are they called Daigaku Imo – literally means “University Potato”.
Because the sweet potatoes were filling and cheap, they became a popular snack at universities in Tokyo during the early 1900s. Until today, Daigaku Imo is still popular and can be found at many food stands and school festivals during the fall season.
Japanese Sweet Potatoes (Satsumaimo)
The Japanese sweet potatoes have this beautiful creamy yellow flesh on the inside and burgundy skin on the outside.
You can get these Japanese sweet potatoes at Japanese grocery stores, Asian grocery stores (especially Chinese and Korean), your local farmers markets, and even at Trader Joe’s, especially during fall and winter months.
How to Make Candied Sweet Potatoes
It’s very simple to make this snack. Here are the 5 easy steps!
- Cut Japanese sweet potatoes into big bite-size pieces.
- Deep fry till golden brown and crispy.
- Make candy syrup.
- Coat the fried sweet potatoes in the caramelized syrup.
- Sprinkle black sesame seeds and let cool.
3 Basic Tips for Candy Making
Here are some tips when you make the sugary syrup for candy coating:
- Combine your sugar and water off the heat, and stir until the sugar is evenly moistened.
- Avoid stirring the sugar once it starts cooking as agitation can cause the sugar to crystallize.
- Use acids (lemon juice and vinegar) to prevent crystallization.
Bonus: Healthier, Non-Deep-Fried Version
For the best tasting Daigaku Imo, deep-frying is always the way to go. But if you wish to avoid deep frying, there is a shortcut you can take.
I learned about this steam & shallow-fry technique from a friend and decided to give it a shot. At first, I was skeptical. But the result was so good that I was blown away. Not bad for non-deep-frying method, I’d say. If you are not going to deep fry, this might be your only favorite way to enjoy the sweet potato snack!
In the recipe instructions below, you’ll find both deep-frying and shallow-fry methods. Just don’t forget to grab a bag of Japanese sweet potatoes the next time you see them at your local market.
Watch How To Make Daigaku Imo (No Deep-Frying Version)
Japanese candied sweet potatoes (Daigaku Imo) covered in a sugary coat and garnished with black sesame seeds.
Japanese Ingredient Substitution: If you want to look for substitutes for Japanese condiments and ingredients, click here.
Candied Sweet Potatoes
#1 Deep-Fry Version
- 1.2 lbs Japanese sweet potatoes (Satsumaimo) (2 pieces)
- 2 tsp kosher/sea salt (I use Diamond Crystal; use half for table salt) (for soaking sweet potatoes)
- 2 cups neutral-flavored oil (vegetable, rice bran, canola, etc) (for deep frying)
- 5 Tbsp sugar
- 1 ½ Tbsp water
- 1 Tbsp mirin (substitute: ½ Tbsp sugar)
- 1 tsp rice vinegar (vinegar helps the sugar from hardening when it cools down)
- 1 tsp soy sauce
- 1 tsp toasted black sesame seeds (for garnish)
#1 Deep-Fry Version
- Gather all the ingredients.
- Carefully wash the sweet potatoes (Don’t peel the skin). Cut the sweet potatoes diagonally while rotating the sweet potato a quarter between cuts. This Japanese cutting technique is called “Rangiri”.
- Put the sweet potatoes in 8 cups water and add 2 tsp salt. Soak for 15 minutes to remove starch.
- Add the oil in the medium pot (I use a 2.75-QT Staub) and bring it to 320ºF (160ºC) (Use a cooking thermometer helps!). Meanwhile, dry the sweet potatoes with the kitchen towel (or paper towel).
- When the oil has reached 320ºF (160ºC), add the sweet potatoes (half of them) into the oil and deep fry. Do not crowd the pot and fry in batches (I do twice).
- Deep fry until golden brown, about 10 minutes.
- When it's golden brown, insert a wooden skewer to make sure it goes through. Transfer to a wire rack or a paper towel to drain the oil.
- To make candy (syrup), combine 5 Tbsp sugar, 1 ½ Tbsp water, and 1 Tbsp Mirin in a large frying pan off the heat. Put on the stove and bring it to boil on medium heat.
- Once the mixture is bubbling, add 1 tsp vinegar and 1 tsp soy sauce.
- Reduce the mixture, stirring constantly, until the right consistency. When you can draw a line on the pan, add the sweet potatoes.
- Turn off the heat and coat the sweet potatoes with syrup. Sprinkle black sesame seeds (once the candy is hardened, sesame seeds won't stick to the surface, so do it while candy is soft).
- Serve on a plate or bowl. Enjoy!
#2 Steam & Shallow-Fry Version
- Gather all the ingredients.
- Carefully wash the sweet potatoes (Don’t peel the skin).
- Cut the sweet potatoes diagonally while rotating the sweet potato a quarter between cuts. This Japanese cutting technique is called “Rangiri”.
- Soak sweet potatoes in water for 15 minutes to remove starch.
- Do not heat the frying pan yet. Add sugar, oil, soy sauce and rice vinegar in the pan and combine all together.
- Dry the sweet potatoes completely with paper towel and place in the pan.
- Wrap the frying pan’s lid with kitchen cloth. This is to prevent condensation on the lid dripping into sweet potatoes while cooking.
- Cover with the lid and turn on the heat to medium.
- When you hear bubbling sound from the pan, turn the heat to low to medium-low, and set timer for 2 minutes. Open the lid and flip the sweet potatoes every 2-3 minute so that all sides will have nice golden brown color and get flavored.
- Depends on the size of sweet potatoes, the cooking time varies, cook for 8-10 minutes or until an inserted skewer goes through smoothly (I personally prefer it a bit tougher than completely soft texture). Transfer to the serving plate/bowl and sprinkle black sesame seeds.
Other Japanese Sweet Potato Recipes
Editor’s Note: This post was originally published on October 15, 2013. The post has been updated in January 2020 with the recipe for the traditional method and with new images.