Soak the kazunoko for 2 hours in a bowl of water with a small amount of salt, replace with water, then soak for 2 more hours to remove excess salt.
When the salt has been reduced to a subtle amount, carefully remove the white membrane on the surface of the kazunoko with the pad of your thumb. The kazunoko on the left shows what it should look like after it is removed.
Put the sake into a pot, then heat to evaporate the alcohol. Add the rest of the marinade ingredients, bring to a boil, then cool to the touch.
Add the kazunoko from Step 2 to the marinade, then allow to soak for 1/2 a day, then it's done. If you wrap them tightly with plastic wrap to press them down into the marinade, you don't need so much of it.
Sprinkle on some bonito flakes or powdered gold leaf to dress it up.
I updated a variety of the photos for various recipes. See Recipe ID: 2438681.
Story Behind this Recipe
Unlike the blackish kazunoko I ate in the Kanto region of Japan that tastes like it's boiled, I wanted to create a beautiful looking kazunoko with a crunchy texture.
Dashi stock made only with bonito tends to darken the kazunoko, so it's best to use a blend.
When removing the white membranes, be careful not to break the roe apart.
When marinating, it's best to put the kazunoko into warm marinade close to body temperature, rather than cold, so that it will absorb evenly and quickly.
Do not take the kazunoko out of the marinade until serving.