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Negitoro onigiri (rice ball) on a gray plate with green brushstroke design, with mashed tuna and chopped green onions in a rectangular plate the background

Negitoro Onigiri (Minced Tuna Rice Ball)

Prep Time30 minutes
Total Time30 minutes
Author Yuto Omura
Servings 4 rice balls

Ingredients 
 

Instructions 

  • Optional step for improved texture & flavor: Shiojime. Wash and dry 60 g sashimi grade tuna block, then sprinkle with salt all over and place it in a container. Store the container in the fridge for 10-15 minutes with one side elevated to drain the excess moisture. Wash off the salt and pat the surface dry with kitchen paper.
    salted tuna in a steel rectangular container propped up on one side to allow excess moisture to drain to the bottom
  • Use a spoon to scrape the tuna flesh.
    scraping block of sashimi grade tuna with a spoon to make negitoro
  • Chop with a knife until it becomes roughly mashed.
    Roughly chopping sashimi-grade tuna on a wooden chopping board to make negitoro
  • Place the mashed tuna in a bowl and add ½ tbsp Japanese mayonnaise, ½ tsp cooking oil and ⅛ tsp dashi granules. Mix until evenly distributed.
    mashed sashimi-grade tuna mixed with oil, dashi granules and mayonnaise in a bowl
  • Measure out 440 g cooked Japanese short-grain rice and divide it into equal portions. If using a rice ball mold, sprinkle a pinch of salt into the mold and add half a portion (approx 55g / 2oz) of rice. Make a dent in the center and add a spoonful of mashed tuna.
    Mashed tuna (negitoro) in rice in a plastic onigiri (rice ball) mold on a white background
  • If shaping by hand, wet your hands and sprinkle them with a pinch of salt. Take a portion of rice (approx 110g / 4oz) and spread it flat on your palm, placing a spoonful of mashed tuna in the center.
    a moving image showing how to add fillings to onigiri rice balls
  • Top the tuna with a small blob of wasabi and a few finely chopped green onions. Add 1 drop of Japanese soy sauce (koikuchi shoyu).
    Pouring soy sauce over negitoro onigir in a plastic rice ball mold on a white background
  • For the mold, add the other half of the rice on top and sprinkle with a pinch of salt. For hand-shaping, fold the rice over and then shape into a rounded triangle.
    sprinkling the surface of negitoro rice ball with a pinch of salt
  • Wrap with nori and serve right away. Enjoy!
    Negitoro onigiri (rice ball) on a gray plate with green brushstroke design, with mashed tuna and chopped green onions in a rectangular plate the background

Notes

The rice temperature: Steaming-hot rice starts to cook the outside of the tuna, a filling meant to be eaten raw. Rice left to cool completely loses its stickiness and is hard to shape.
Why mayonnaise, oil and dashi granules: Chopped on its own, lean tuna stays dry, its iron-like flavor takes over, and every bite tastes the same. Both fats turn it into a smooth, creamy filling, and the dashi granules add umami of their own.
Keep the wasabi on top: Stirred into the filling, wasabi spreads thin through every bite. Left in one spot on top, it gives you bites with a real kick and gentler bites in between.
Eat them as soon as they are made: These rice balls are a poor fit for the freezer. Frozen mayonnaise separates and seeps into the rice. A tuna block that has been thawed once never goes back in the freezer.
Buying tuna in the US: The cheapest lean block is all you need, as long as the label says it is safe to eat raw. Look for yellowfin or bigeye. Both are often sold as ahi.