Slowly roasted sweet potato at low temperature is the most delicious and healthy snack that Japan offers. The subtle burnt sweet aroma coming from a street food truck in Japan is just irresistible. And the good news is that we can achieve this at home.
What is Yaki Imo?
Those baked or roasted Japanese sweet potatoes are called “Yaki Imo” or “Ishi Yaki Imo”. Ishi yaki imo is sweet potato baked in hot stones or pebbles. Surprisingly roasted sweet potato is consumed as a snack rather than a side dish in Japan. There are many yakiimo street venders in Japan selling delicious freshly baked sweet potato by its weight.
Especially in winter, you will see the Yaki Imo or Ishi Yaki Imo sold everywhere in Japan. Hearing a Yaki imo food truck coming around (because they call out with speaker) is a typical Japanese winter scene. Why is sweet potato sold more in winter? Because sweet potatoes are harvested in autumn.
Types of Sweet potato
Sweet potato is called “Satsuma Imo”. It is named after Satsuma Region in Kyushu island where the sweet potato was first introduced to Japan. When the Japanese refer to sweet potato, they are the purple sweet potatoes with white flesh. The white flesh turns a beautiful golden yellow colour when it is cooked.
A well-known sweet potato for roasting is “Naruto-Kintoki” and “Annou-imo”. Even though we can get purple sweet potatoes outside of Japan, those particular types are not readily available.
Baking/Roasting Methods
But don’t despair. There are ways to cook sweet potatoes just like the stone-baked roasted potatoes you can buy from the street food truck in Japan. And it is just so simple! NO matter what equipment you use. Baking sweet potatoes slowly at low temperature is the key for deliciously sweet baked sweet potatoes.
Sweet potatoes contain a lot of enzymes called amylase. This amylase breaks down the starch into sugar at temperatures up to 65°C (150°F). Thoroughly baking at low temperature increases the enzymatic action and breaks down many starches into sugar thus increasing the sweetness.
1. Choosing good sweet potato
How to pick a good sweet potato suitable for roasting at home? Choose ones that are plumply round 6-8 cm (2.5-3 inch) in diameter and both ends are not shrivelled. The skin is smooth and vivid and uniform in colour. Furthermore, sweet potatoes with fewer hair roots will have smooth texture.
2. Oven roast
Wash sweet potatoes and wrap them tightly with aluminium foil. Place them in an oven. You don’t need to preheat the oven. Set the temperature at 160°C (320°F) and bake them carefully for about 90min. Test by inserting a skewer, if it is soft turn the oven off and leave them in the oven for another 10 minutes.
3. Frying pan roast
This is the method I used. Wash the sweet potatoes and wrap with alfoil tightly. Arrange them on a frying pan or a skillet. Place a lid over and roast for about 50 to 60 minutes. Turning the sweet potatoes every 15 minutes. Turn the heat off when the softness is checked with a skewer. Leave the sweet potatoes to rest.
Handy glove “Gunte”
Those cotton gloves are called “gunte” (pronounced like goo-n-tay) and are a working glove. They become very handy when you need to handle hot food. I often use these working gloves in my cooking. You see this in making the extra thick and fluffy Japanese pancakes too.
Other sweet potato recipes to check
- Japanese candied sweet potato “Daigaku Imo”
- Japanese rice porridge with sweet potato
- Pureed Sweet potato and chestnuts “Kuri Kinton”
- Christmas Sweets : Edible Pine cones
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Roasted Sweet Potato
Equipment
- a frying pan/a skillet
- aluminum foil
Ingredients
- 3 purple sweet potatoes *1
Instructions
- Wash the sweet potatoes
- Wrap the sweet potatoes with aluminium foil tightly.
- Arrange the aluminium foil wrapped sweet potatoes on a frying pan or a skillet over low heat.
- Place a lid over the frying pan or the skillet and roast the sweet potato slowly for about 1 hour. *2
- Turning the sweet potatoes about 90 degrees every 15 minutes.
- Insert a skewer, if the sweet potatoes are soft, turn the heat off and serve.
Tim says
As an Army brat in the 1950’s, my sister and I experienced eating these Yaki Imo sweet potatoes many times over the years we spent on Grant Heights base, Tokyo. Chanting and a horn or bells would announce the arrival of a beautifully painted cart, pulled by 3 Japanese women in white face and traditional garb and headgear. The driver who walked behind was dressed maybe like a Kabuki actor, white face and thick colorful robe. From this cart we would buy the Yaki Imo as well as roasted chestnuts. I really miss the late autumn/winter where they would show up perhaps 3 times every year.
Shihoko | Chopstick Chronicles says
Hi Tim, Thank you for sharing your stories in Tokyo. I miss those chanting and horn and delicious street food Yakiimo in Japan.
Nicole says
Living in Japan (for a total of nine years), this was my favorite cold weather snack and I loooved how it’s scent would draw me in from the automatic doors of YouMe Town. Thank you for sharing this cooking process so I can now enjoy these again!
Shihoko | Chopstick Chronicles says
You are welcome Nicole 😀
Lisa says
When i fry pan it, should the heat be on low?
Shihoko | Chopstick Chronicles says
Hi Lisa Yes.
James says
Really looks tasty and delicious. I ate sweet potato last few weeks but its not good like this because its hard a little and bland. Maybe my process of cooking those sweet potato its not good. But I’ll definitely try this later because I still have few sweet potato. I will also cook this for my friend. I’m sure she will love this.
Shihoko | Chopstick Chronicles says
Thank you for your lovely comment 😀
Allison says
Ah I used to always look forward to じゃがいも season in Japan! Nothing beats the wonderful smell of yaki imo in the air when you’re walking down the street in autumn/winter. Plus, it’s always this time of the year when konbinis start rolling out jagaimo flavoured snacks…yum!
Now I live in China and even though we have a similar variety here and also baked the same way, my heart still belongs super yellow and purple yams I would have in Japan.
Thanks so much for sharing this classic!
Shihoko | Chopstick Chronicles says
You are welcome Alliosn 😀 Thank you for sharing your story.
Mya Murphy says
I’ve never heard of this but it sounds seriously scrumptious!
Shihoko | Chopstick Chronicles says
Hi Mya, Ies indeed 😀
Fatima says
Can’t wait to try this!
Shihoko | Chopstick Chronicles says
This is addictive 😀
Brandon Sparks says
Now to have this with dinner would make it a perfect meal.. Yummy..
Shihoko | Chopstick Chronicles says
Yes Brandon definitely 😀
Ashley says
So easy and delicious! We will definitely make these again.