Karashi Mentaiko Onigiri (Spicy Cod Roe Rice Ball) Recipe

Gather the ingredients.

Cut a medium-sized piece of plastic wrap and lay it flat on a clean cutting board. Gently sprinkle the plastic wrap with a bit of Kosher or sea salt. This step is optional, but the additional salt on the exterior of the onigiri is very common. 

Scoop warm, cooked rice onto the center of the plastic wrap in a heaping pile. Slightly flatten out and spread the rice so that you can easily imprint a thumb into the center of the rice. The technique is similar to making thumbprint cookies.

Cook the karashi mentaiko by placing it in a small bowl and covering it with plastic wrap, then microwaving it on high for 10 to 15 seconds or until cooked through. The mentaiko will change in color from a deep, translucent pinkish-red to a pale, solid light pink color.

In the indented center of the rice, place a piece of cooked karashi mentaiko. Next, take the ends of the plastic wrap and slowly bring the ends of the plastic wrap together as the rice encloses the karashi mentaiko filling. 

Next, gently squeeze the onigiri in your hands by cupping your hands together. Gently rotate the onigiri in the triangular-cupped shape of your hands, while gently flattening the center at the same time by pressing your fingers into the rice ball. You’ll achieve a thick, yet almost flat triangular shape.

Unwrap the plastic wrap from the onigiri. Use the dried seaweed sheet to wrap around the onigiri. Enjoy immediately or wrap in a clean sheet of plastic wrap to pack in a bento or lunch box.