Sweet Potato Tempura Onigirazu

Sweet Potato Tempura Onigirazu
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I, like most of the world, have a nearly insatiable taste for sushi. I didn’t have my first piece of maki until I 16 but I have more than made up for lost time in the 16 years since. As with most of my favorite foods, I have tried my hand at sushi in the past. My attempts have been serviceable but nowhere near restaurant quality. It’s the rice, I can’t get it right. And, of course, my lack of dexterity holds me back as well. My maki rolls lack structural integrity, so much so that I often find myself eating the evidence of a poorly executed roll, leaving me prematurely full and my serving platter woefully empty. This is why I love these Sweet Potato Tempura Onigirazu. They don’t require a deft hand or perfectly seasoned sushi rice and they crush my sushi cravings, without destroying my confidence.

Sweet Potatoes cut into medallions

Onigirazu has been an internet darling for some time now. But in case you’ve been out of the nori loop, allow me to enlighten you. Onigirazu is essentially a rice sandwich bundled in a sheet, or in this case sheets, of nori. It is sometimes referred to as a sushi sandwich, which is technically incorrect because the rice is typically unseasoned. Seasoned rice is central to the proper definition of the word “sushi”. So a rice sandwich is actually a closer approximation.

Adding egg yolks to make tempura batter
Rolling the Sweet Potato Medallions in Cake flour

The onigirazu first appeared in a popular Japanese manga called Cooking Papa in 1991. Yes, you read that correctly, this dish owes its existence to a comic book series. 20 years later, onigirazu made the jump from page to bento box and quickly became a household favorite throughout Japan. It naturally made its way into the blogosphere via YouTube, Instagram, and the like. And now it’s here and I am so glad it is.

Sweet Potato Tempura freshly fried

As far as fillings go the sky seems to be the limit. I’ve seen all manner of things slipped into these nori parcels. I chose to go the sweet potato tempura route because I had many wrongs to right in that department. I’ve been trying to make good sweet potato tempura since I was a teenager and, well, it’s never gone so well. Well, not until this round.

Sweet Potato Tempura

Everything I got right about this sweet potato tempura I owe to the book Japanese Soul Cooking. I have attempted tempura many times in the past and they have ranged from good to meh to compost-worthy. Sweet potato tempura in particular has eluded me. The worst sin I’ve committed against this beloved dish is not cooking to potato enough. Most of my batches of sweet potato tempura have been golden on the outside but crunchy on the inside. But no more! This round was crisp on the outside and buttery, melt-in-your-mouth on the inside.

Sweet Potato Tempura Onigirazu stacked and ready to be wrapped

Once you wrap your head around sweet potato tempura, the rest of this recipe is beyond simple. Simpler still if you have a rice cooker. And if you don’t have a rice cooker, I strongly suggest you get yourself one. We use ours 3-4 times a week. I don’t usually go in for single-use appliances, but rice cookers make the best rice – they just do. Other than that all you have to do is chop, slice, and fold your way to an excellent meal. And if you’re concerned about folding an onigirazu, I would urge you to let go of that fear. The plastic wrap really does do most of the heavy lifting.

Sweet Potato Tempura Onigiri

Now, there is one last thing we have to address here and that’s the insane height of these Sweet Potato Tempura Ongirirazu. Onigirazu is not typically this vertically gifted. I was insistent that each sandwich have three pieces of tempura and half an avocado. Was that the right call? Probably not from an aesthetics standpoint but in terms of flavor I wouldn’t have it any other way. You are of course welcome to scale your onigirazu back. But I think you can handle the towering majesty of my far too giant onigirazu. Just be sure to have an extra sheet of nori ready, you’re going to need it.

Sweet Potato Tempura Onigirazu

So that’s everything you need to know about this Sweet Potato Tempura Onigirazu. A rice sandwich that is admittedly hard to get your mouth around but well worth the fight.


Sweet Potato Tempura Onigirazu

Sweet Potato Tempura Onigirazu

These mile-high Sweet Potato Tempura Onigirazu feature layers of crisp tempura, creamy avocado, and refreshing cucumber all bundled in rice and nori.
Prep Time 30 minutes
Cook Time 30 minutes
Rice Soaking Time 30 minutes
Course Main Course
Cuisine Japanese
Servings 4


  • A large dutch oven
  • Candy Thermometer


  • 1 cup uncooked sushi rice
  • 2 sweet potatoes cut into medallions
  • cups cake flour divided
  • 1 quart neutral oil I used canola oil
  • 2 egg yolks
  • 2 cups cold water
  • 4 ice cubes
  • salt for sprinkling
  • 8 sheets nori
  • 3 mini cucumbers sliced lengthwise and halved crosswise
  • 2 avocados thinly sliced
  • kewpie mayo for drizzling
  • black sesame seeds for sprinkling
  • plastic wrap for forming


  • Place the rice in a fine-mesh strainer and rinse under cold water until the water runs clear. Place the rice and the strainer in a bowl filled with cold water and let soak for 30 minutes.
  • After 30 minutes have passed, place the rice in a rice cooker or a small saucepan. Add 2 cups of water or the amount of water required by your rice cooker. Either let your rice cooker do the work, or bring the water and rice to a boil, then reduce to a simmer. Cover and let cook for 20 minutes or until the rice is tender and most of the liquid has been absorbed. Keep the cover on the rice and let steam for 10 minutes more.
  • Place 1/2 cup of the cake flour in a large shallow vessel, like a pie plate. Roll the sweet potato medallions in the flour until coated. Set them aside. Pour the oil into a large dutch oven fitted with a candy thermometer and begin heating the oil to 360°F.
  • While the oil is coming up to temperature, make the tempura batter. In a large bowl, whisk to combine the egg yolks and the water. Add the ice cubes and set the bowl aside. Sift in the remaining flour and, using chopsticks, mix the batter until it resembles a thin pancake batter. It should be lumpy, resist the urge to over mix.
  • Once the oil is ready, begin dunking the medallions into the batter before adding them to the oil. Work quickly. You don't want the batter to hang around too long and get warm. Fry the medallions for 6-8 minutes, rotating frequently. Transfer the finished tempura to a plate lined with paper towel and sprinkle with kosher salt. Keep the tempura warm in a low oven (150°F) until you're ready to build your onigirazu.
  • Place a sheet of nori in the center of a large piece of plastic wrap. Working with wet hands to keep the rice from sticking, place 1/3 of a cup of rice in the center of the sheet. Flatten the rice with a wet hand.
  • Cover the rice with cucumber slices in an even layer. Top the cucumber with three pieces of sweet potato tempura and finish the sandwich with half of an avocado, a drizzle of mayo, and a sprinkling of black sesame seeds.
  • Place 1/3 cup of the rice on top of the fillings and once again flatten it with a wet palm. Place another sheet of nori on top, tucking the sides and corners around the filling. Fold each corner of the plastic wrap and bottom nori sheet towards the center and wrap tightly to form a seal. Using a serrated knife cut the onigirazu in half and serve.


Tempura recipe adapted from the book Japanese Soul Cooking
Keyword avocado, cucumber, nori, rice, Sweet Potato, tempura

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