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Mentaiko onigiri with one cut in half to show the filling on a small bamboo tray on a dark gray wood-effect background with red fabric in the background

Mentaiko Mayo Onigiri

Prep Time10 minutes
Total Time10 minutes
Author Yuto Omura
Servings 6 onigiri

Ingredients 
 

Instructions 

  • Place 50 g spicy cod roe (mentaiko) on a cutting board and make an incision lengthways through the skin using scissors or a sharp knife. Open it up and scrape out the inside with a spoon.
    Mentaiko (spicy roe) scraped out of skin on a wooden chopping board with metal spoon
  • Transfer the mentaiko to a bowl (you can eat or discard the skin) and add 3 tbsp Japanese mayonnaise, ¼ tsp Japanese soy sauce (koikuchi shoyu) and ⅛ tsp dashi granules. Mix until evenly distributed.
    mentaiko onigiri filling in a glass bowl with metal spoon on a white background
  • Divide 700 g cooked Japanese short-grain rice into 100-120 g portions. If shaping by hand, wet your hands and sprinkle them with salt. If using a mold, sprinkle the mold with a pinch of salt.
    two hands rubbing palms with salt
  • To shape by hand, take a portion of rice and flatten it on your palm. Make a dent in the center and add about 2-3 tsp of the filling. If using a mold, fill it up just over halfway with rice and press a dent in the center before adding the filling.
    Japanese rice in an onigiri mold with mentaiko filling
  • If shaping by hand, fold the rice over to seal the filling inside, then press and turn to shape into a rounded triangle. If using a mold, fill it to the top with rice and sprinkle another pinch of salt on top. Press the lid down firmly to shape, then remove it from the mold.
    sprinkling salt over mentaiko onigiri to flavor the outside of the rice
  • Wrap with nori right before eating. Enjoy!
    mentaiko onigiri wrapped with nori held up in hand

Notes

If the filling is runny: Put the whole bowl in the fridge before you shape. The cold firms up the mayonnaise, and the filling is far less likely to ooze out as you press.
Keep the filling to 2-3 tsp per ball: The more you pile in, the thinner the rice around it gets, and the filling squeezes out through the seam while you shape.
Taste the mentaiko first: Its saltiness varies from brand to brand. If yours is on the salty side, use less salt on your hands, and keep salt out of the rice itself.
Shape the rice while it is warm: Freshly cooked rice that has stopped steaming hard is ready for your hands. Once it cools, it sets like clay.
Wrap the nori at the last minute: The longer it sits on the rice, the more steam it takes on and the softer it goes. When you take them on the go, pack the nori separately.
Stick to Japanese short-grain rice: Long-grain rice such as jasmine has no stickiness and will not hold a triangle. If you cannot find Japanese rice, Korean rice comes closest.
If you cannot find mentaiko: Tarako keeps the same grains and loses only the heat, and a pinch of ichimi togarashi (Japanese chili powder) brings it closer. Korean myeongnan-jeot is saltier, so go easy on the salt for your hands.
If you have no Kewpie: Stir a few drops of rice vinegar and a tiny pinch of sugar into regular mayonnaise. The filling already carries dashi granules, so the mayonnaise needs no dashi of its own.