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Onigiri... Japan's Best Kept Secret: Tuna Mayo Onigiri Recipe

Updated: May 31, 2023

Our family's favorite onigiri recipe.

Move over boring lunchbox sandwich because onigiri is here with equally endless filling options. Often triangular in shape, onigiri is basically a ball of sticky white rice enveloping a savory filling. Flavors range from the universally appealing tuna mayo or grilled salmon to more unique flavor combinations, such as dried bonito flakes, pickled plum, and even fish eggs with cream cheese.

Store-bought onigiri is usually presented in a clever (and initially puzzling) 3-step plastic wrapping system that keeps the onigiri fresh and prevents the nori (dried seaweed) wrap from becoming soggy. Once you figure out the art to unwrapping it, the genius of the onigiri wrapping system becomes apparent-- layers of plastic carefully folded outside and in between the onigiri’s ricey body and nori (dried seaweed) wrapper. When done successfully, the plastic wrap slides out gracefully from in between the layers leaving a perfectly crisp, intact nori wrapper and fresh ball of rice. One of the best places in Japan to find onigiri (among other delicious treats) is at the local convenience store or “combini.” But if you aren’t located close to a Family Mart or Lawson’s, you can still enjoy delicious and fresh onigiri at home.

Even if you aren’t ready to completely abandon your PB&J obsession, making onigiri is a delicious way to add some variety in your lunch box. And it’s a great late-night snack. My youngest son asks for this tuna mayo onigiri at least once a week! Check out the recipe below to try our family’s favorite onigiri recipe.

What You’ll Need-

Note: I do not receive any compensation for products that I mention. I mention specific products for illustrative and informational purposes only (e.g., to provide examples, share what I’ve used in the past, help readers know what types of ingredients to look for. ) Any mention of specific brands, companies, or stores should not be interpreted as an official endorsement.

Rice: As a rule, I cook from scratch as much as possible. This recipe is one exception to that rule. There’s not much utility to a “quick, easy-to-make snack” that requires a semi-lengthy process of steaming rice to perfection. So for this recipe, I use microwavable Japanese short or medium grain white rice (such as Nishiki Premium Grade rice) that comes in 7.4oz container. I prepare it according to the package directions then let it cool slightly before forming my onigiri.

If you decide to steam your own rice instead of using microwavable rice: You can definitely steam your own rice using a bamboo steamer basket, stovetop pot, or electric rice steamer, if you prefer. Just make sure that you are using good, Japanese short or medium grain white rice (like Koshihikari and Nishiki). It may or may not also say “sushi rice” or “sticky rice” on the package. The specifics of steaming rice vary based on your chosen method of preparation (and this isn’t a rice steaming tutorial!) so be sure to do your research ahead of time. Consult the instructions that came with your rice steamer appliance if you plan to use one. For most methods of preparation, you’ll need to rinse the rice several times in cold water until the water runs clear and soak it for at least 2 hours before steaming. (Another, time consuming reason to use microwavable rice instead.)

Another note on onigiri rice: To hold its shape, your onigiri rice needs to be the right consistency. It can’t be too soggy and mushy. It can’t be too dry and hard. Just like the three little bears, it needs to be just right. So, if you haven’t perfected your rice making skills, it’s probably best to use microwavable Japanese rice, at least until you get comfortable with forming the onigiri.

Tuna (or Salmon): I’m guessing you don’t ground up fresh peanuts every time you make a PB&J. And, I don’t bake fresh fish every time I make onigiri. We regularly eat baked or grilled salmon and tuna at our house. Leftovers from yesterday’s lunch or dinner make a great filling for onigiri. However, in a pinch canned tuna also works just fine. Just make sure you drain it.

Kewpie Mayo: Smooth, tangy, slightly sweet Japanese mayonnaise, Kewpie mayo is fairly easy to find in most grocery stores in the US (and obviously in Japan.) A quick internet search will reveal many recipes for making your own kewpie mayo at home, ranging from scratch-made kewpie mayo using egg yokes to simpler recipes for converting the jar of Dukes (or Hellman’s) that you already have in your refrigerator.

Hondashi: I started adding hondashi (a flavor seasoning of dashi granules) to my onigiri filling to add the umami flavor that seemed to be missing in my earlier attempts to recreate the flavors I remembered of the onigiri in Japan. In the US, Hondashi can be found in Japanese or Asian specialty grocery stores. In Japan, it’s available in most grocery stores. (I’m guessing you can also find it online.) Hondashi comes in several different flavors, like bonito, kombu (kelp), and iriko (sardine), and in combinations of these flavors (like bonito + kombu.) One box of hondashi can make many onigiri. Several small paper packages come in a box and you only need to use a pinch for each onigiri. The granules dissolve on their own with the small amount of liquid that remains in your tuna after you drain it. If your fish is on the dryer side, you can dissolve the granules with a tiny bit of water before adding them into the mix. You can, of course, skip the hondashi or add your own source of umami to the mix.

Nori (Dried Seaweed): If you want the full-on, wrapped-look, full sheets of nori that come perforated into easy-to-tear strips are best. (Like you’d buy for making sushi.)

Sometimes, I use nori flakes and mix them right in with the rice before putting the onigiri together. The green flakes are super cute (and the flakes are even easier to use than the nori sheets.) Nori flakes are a little harder to find in grocery stores in the US, but you can usually find them in Japanese or Asian specialty stores (or online.) The flakes also come in different flavors/varieties, which can add a burst of flavor to your onigiri experience. (Especially fun if you can’t read the package!)

Onigiri mold and plastic storage containers (optional): Japan is really good at doing simple and convenient without compromising quality. So (quite predictably), affordable, user-friendly onigiri molds and carrying containers can be easily found at common lifestyle stores throughout Japan and also online through websites such as Amazon. While these tools can be really helpful (especially for onigiri neophytes), special equipment isn’t absolutely necessary. In fact, simple plastic wrap (e.g., Saran wrap) or even wet bare hands can be just as effective in shaping your onigiri.

Note: If you plan on storing your onigiri in a plastic container that is specially made for carrying and storing onigiri, make sure that your mold and your storage container are the same size and shape. If you are not using a mold, use your storage container as a guide as you prepare and shape your onigiri. With practice, this becomes easier.


Tuna Mayo Onigiri Recipe

Yield: 2 Onigiri (You will have leftover filling.)

Before you begin: Gather all materials and place out on the table where you will be assembling your onigiri. If you are not near a sink, place a small bowl of water nearby for keeping your hands and utensils moist, as needed. Sticky rice is actually sticky, so it’s important to your fingers and utensils wet when working with it.


· 1 (7.4 oz) package Nishiki (or similar brand) microwavable premium grade white rice

· 1 (5 oz) can of tuna (or baked tuna filet)

· Pinch of handashi (dashi granules)

· 1 Tbsp of kewpie mayo

· 2 strips of nori/dried seaweed (taken from 1 full sheet)


Step 1: Tear two sheets of plastic wrap approximately 8 inches long and lay both sheets side-by-side, flat on the table. Tear two strips of nori following the perforated lines. (Each strip will be approximately 8 x 1.5 inches). Lay one strip of nori on each piece of plastic wrap. Set aside.

Note: You can place your nori sheet directly into the onigiri mold before adding your rice. However, there is a higher risk of tearing the nori with this method. We prefer to wrap our onigiri after it forms. (See step 7.)

Step 2: Cook rice according to package directions. Keep rice covered and cool for 5 minutes.

Step 3: While the rice is cooling, add well-drained tuna, a pinch of handashi, and 1 Tbsp of kewpie mayo to a small bowl and mix thoroughly with a fork, breaking up any large chunks of tuna as you mix.

Step 4: Moisten your fingers and a small spoon with water. Using an onigiri mold, fill the bottom of the mold with a layer of sticky rice approximately 75 mm or ¼ inch thick. The bottom of the mold should not be visible, but you should also avoid layering the rice too thick (otherwise, you won’t have room for filling.)

Step 5: Using a small spoon, place a small heap of the tuna mayo mixture into the center of your rice. Be careful not to overfill to avoid leakage. The exact amount will depend on the size of your mold or palm, though usually will not exceed a teaspoon.

Step 6: Re-wet your spoon and fingers before adding your top layer of rice. Carefully and patiently place rice on all sides of your tuna mayo (between the tuna mayo and the side of your mold.) Then add a layer of rice on the top, ensuring adequate coverage. You shouldn’t be able to see the filling at this point.

Step 7: Add the top of the mold and press down with light to moderate pressure. Do not press too hard. Once shaped, lightly press on the bottom of the mold to release the onigiri into the sheet of plastic wrap that you prepared with nori.

Step 8: Fold the bottom strip of nori around the sides of your onigiri so that the nori fully encircles your onigiri. Then finish wrapping the completed onigiri with the remaining plastic wrap so that it is fully covered.

Optional: If using an onigiri shaped plastic travel container, carefully transfer the onigiri from your mold to the container. (Make sure the container and your mold are the same size!) Trim any excess plastic wrap that may stick out from the container once it is closed.

Step 9: Refrigerate for 30 minutes to allow the onigiri to firm.

Step 10: Enjoy!

Storage: Onigiri is best consumed within 24 hours. Refrigerate (or store in an insulated lunch box with an ice pack) until ready to eat.

Make Ahead: If you want to make your onigiri the night before, it’s best to leave the seaweed off and add it in the morning.


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