Soak fresh kazunoko in cold water for two days, changing water once daily. Store in the refrigerator. This removes the salt from the roe, as well as to loosen the membrane surrounding the roe.
Gently remove membrane from the kazunoko pieces. There is a very thin membrane you will notice after about one day of soaking the kazunoko in water.
Store kazunoko in cool water.
In a small pot, soak dashi konbu in water for about 1 hour.
Bring dashi konbu and water to a gentle boil. Add dried bonito dashi and soy sauce and simmer for about 10 minutes.
Allow the cooked broth to cool. Discard dashi konbu.
Gently break apart kazunoko into bite-sized pieces using your hands. Do not cut.
Place the pieces of kazunoko into the dashi broth and place in the refrigerator 1 to 2 nights while the roe absorbs the flavor of the dashi.
Recipe by Bebe Love Okazu at https://bebeloveokazu.com/2013/12/31/kazunoko-herring-roe-osechi-ryori/