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Friday, May 27, 2011

Roasted Japanese Sweet Potatoes

Have you ever had Japanese sweet potatoes? I didn’t know what they were until they showed up in my CSA bag one week. I mentioned them quickly in a weekly menu post previously, but I would like to talk about them a bit more and share how to make roasted Japanese sweet potatoes, which are pretty much heaven on a plate.

Picture of a roasted Japanese Sweet Potato with salt and pepper from Jane Maynard at This Week for Dinner

What are Japanese Sweet Potatoes?

So what are Japanese sweet potatoes anyway? Apparently Olivia Munn thinks they are the fountain of youth. I just think they are a super healthy, crazy delicious tuber that you should definitely buy if you ever see them at the store or as an option in your CSA. They are a sweet potato with brown or red skin and whitish flesh that turns yellow upon cooking. We found Japanese sweet potatoes to have a buttery, almost squash-like flavor that is divine and their texture is a little bit different than other sweet potatoes. We like to roast Japanese sweet potatoes, cut them in half and top with butter, salt and pepper. Simple, healthy and delicious. (Click here to read more about the history and origin of Japanese sweet potatoes, it’s pretty interesting!)

How to prepare Japanese sweet potatoes for roasting from This Week for Dinner

What do you do with Japanese Sweet Potatoes?

Once I discovered how delicious Japanese sweet potatoes are, I ordered a whole bunch from my CSA. To preserve them IΒ  roasted all of the sweet potatoes at once, placed in freezer bags after they cooled and then stored them in the freezer. I don’t know about you, but one of my major barriers to eating sweet potatoes is remembering to start cooking them early enough to actually have them done by dinnertime. Which is why I’m super excited to have a whole bunch already cooked and ready to go in the freezer. As long as I remember to defrost them when we need them, I think we should be good to go!

What Japanese sweet potatoes look like from This Week for Dinner

The process for roasting them is super simple, but I will share the “recipe” below so you can replicate how we cooked them (and so I can remember what I did myself!). Seriously, if you ever see these at your market, grab a few and give them a try. Nate and I really love them, but they are kind of hard to find.

Roasted Japanese Sweet Potatoes
Prep time
Cook time
Total time
Cuisine: Side Dish
  • Japanese sweet potatoes (as many as you want to eat!)
  • Butter or olive oil or coconut oil
  • Salt and pepper
  1. Preheat oven to 400ΒΊ F.
  2. Wash Japanese sweet potatoes then poke them with a fork in several places.
  3. Place prepared sweet potatoes on a rimmed cookie sheet or roasting pan. place on a cookie sheet or roasting pan. Cook for approximately 1 hour, until knife pierces sweet potatoes easily.
  4. Cut open, drizzle with butter (or olive oil or coconut oil if you want to keep things vegan and dairy free!), salt and pepper and enjoy!




  1. 1

    The good news is that, time-wise, you can always peel them, cut them into cubes, and toss with butter or olive oil and whatever seasonings you want. Then roasting only takes about 20 minutes and each piece has a little caramelization on the outside and is soft on the inside. πŸ™‚ I do this for my kids’ lunches a lot, too — often I’ll even cut the peeled potato into planks, then use small metal cookie cutters to cut out little sweet potato shapes, which I roast and then pack for them. They love it.

  2. 2

    if i dont have time to make a sweet potato for an hour i will poke it and put in the oven for about 30 mins and then pop it in the microwave for about 5 mins and it is PERFECT!

  3. I love these sweet potatoes, but I’ve never thought of freezing them. Like Jillian’s tip, too.

  4. 4

    You can also slice them in 1-1.5 inch rings, boil them for a few minutes and viola! They don’t caramelize, but still tasty. Cook cubes with your rice next time. Yum!

  5. 5

    Have you ever tried baking potatoes in the crockpot? Totally works and they come out divine! I just wrap the potato (red, russet, sweet, whatever) in foil, pile them in the crockpot and cook on low for several hours. It doesn’t help the last minute thing but if you know what you’re cooking that night and the dinner hour is rushed you can put these puppies in early in the day and you’re all set!

  6. 6
    Charlie Sommers

    I lived in Tokyo for eight years back in the 60s and early 70s. I have many fond memories of the oimo-man who came by my home often. His potatoes were reasonably priced (cheap) and packed in warm gravel to retain the heat. My Japanese wife and I would have considered it sacrilege to have added anything, including butter, to his delicious offering.

    Japanese sweet potatoes are widely available at Asian markets across America today and can be enjoyed in a very simple manner. Just roast them and eat them!

    • Jane Maynard

      so glad you commented, I could totally picture your memory! next time I’ll try it without the butter…MAYBE. butter is hard to resist πŸ˜‰

  7. 7
    Charlie Sommers

    Just enjoy them with a cup of, unsweetened of course, green tea. A delicious combination that’s just sweet enough without being cloying and a snack that your heart will thank you for.

    • Okuda

      Hi,may I know what is the usual flesh colour of the Japanese sweet potato? Is yellow and purple the usual flesh colour of this lovely sweet potato?

      Thanks πŸ™‚

    • Okuda – the japanese sweet potatoes we’ve always had have been yellow fleshed. but there may be purple out there, I’m just not sure!

  8. 8

    Nice tip about the microwave.

    Check out my recipe for sweet potato on my blog

  9. 9

    Nice tip about speeding up the cooking in the microwave.

    Check out my recipe for Japanese sweet potato on my blog

  10. 10

    I love these sweet potatoes! For a real time saver, either cooked them covered in water in a pressure cooker on high (15psi) for 7 minutes or on a rack steamed. You’re also cooking at a higher temp with a pressure cooker. we eat them as is. No salt or butter. My two year old twins love them!

    • Jane Maynard

      I was just talking about pressure cookers with a friend at dance class the other day. I don’t have one but sort of want to get one but only remember my mom using it for chicken…but your comment is inspiring me! πŸ™‚

  11. 11

    Hi, why does my sweet potato turn out dry and crackly after roasting at abt 200 degrees, 30-40mins? It’s not soft and moist. Is it because I store them in fridge prior to baking? Please get back to me ASAP. I would like to show you a pic of my sweet potato. I’m so distressed cos I eat them everyday. Thanks for your help.

  12. 12

    Ditto what Jane says. Here’s another resource on storing sweet potatoes, from a master gardener up in Vermont. Easy tutorial:

    Good luck!

  13. 13


    • Charlie Sommers

      Steamed or boiled was the usual preparation method used by my Japanese wife way back when. The average Japanese home of the 1960s didn’t include an oven in the kitchen. Roasted potatoes were available only from the “Oimo man,”

  14. 14

    So delicious, this is literally my go-to dinner for being broke and living in Vancouver ha! Oh and perfect cooking time. The only thing I do/change is wrap them in foil and cook them on top of a pizza pan πŸ™‚

  15. 15

    In Japan yaki imo are often cooked on the stove top in special earthenware pots with a small grill grate inside. This accurately re-creates the traditional flavor delivered by the yaki imo man. Taking the time to bake in the oven at 325-350Β° is the next best thing. Microwave, crock pots and the like are strictly for those who don’t know the difference.

  16. 16

    Try using virgin coconut oil in lieu of butter!

  17. 17
    Joseph Ferrari

    After I cook them, how do I freeze them? When I want to use them, do I defrost them? How do I heat them up? Thanks in advance for your help!

    • once they cooled down, I just stuck them in a freezer bag, whenever I freeze things I try to lay them side by side so they don’t freeze in a giant block. I think I wrapped them in a bit of foil or parchment paper before putting in the bag to keep the sweet potatoes separated.

      yes, defrost them, either put in fridge the day before, let sit on the counter for a couple hours, or defrost on the defrost setting in the microwave. lots of flexibility!

      I just reheat in the microwave to get them hot to eat! πŸ™‚

      hope this is helpful, let me know!

  18. 18

    I made these for Thanksgiving because I could not decide between sweet potatoes and yukons and wanted to experiment and try something new. I decided to roast these as recommended and to speed it up I quartered them lengthwise and added a couple of cubes of homemade chicken stock from the freezer, a dab of olive oil and salt and they were divine. A perfect compromise from the traditional and a new flavor sparks the meal. I confirm butter not needed!

  19. 19

    I’m with Charlie Sommers. I lived in Gumma Prefecture ’79-’81. Soulful sound of the oumo man crying “Yaki imooooo!” at dusk pushing hi cart. Such a wonderful treat on a chilly autum night. Fondest memories!

  20. I enjoyed reading this and other posts, bookmarked to come back.

  21. 21
    Don Birkholz

    There is a Murasaki Japanese sweet potato developed recently by the Louisiana people and looks exactly like your photo. It is grown mainly in California. (even has a US patent.) So the Japanese sweet potato purchased at the local market may have been bred in the US. I just read about in on the Yahoo web site.

    • hi don! interesting and makes sense. The Japanese sweet potatoes I had were definitely grown in California as I got them through a local CSA. Happy there is a US version of this variety as it is delicious! (I just wish I could find them more often, they are hard to come by!)

  22. 22

    They are readily available at my Whole Foods. I’m on the east coast. Very reasonably priced as well.

  23. We made these yummy dish today for our Thanksgiving celebration on Vashon Island. Your sweet potatoes were a hit even with kids, everyone loved it ??

  24. 24
    Ann Williams

    I love the Japanese sweet potatoes. I bake them, split them open and slather almond butter all over them. Add a steamed veggie and dinner is complete. (No, I’m not a vegetarian; just love this combination!)

  25. 25

    Hi, if anyone want to buy Japanese red & yellow purple sweet potatoes, can buy from Bangladesh where can buy very testy potatoes with cheap money.

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