Grab a large pot and fill it about halfway with water.
Bring it to a simmer, then place a steamer basket over it.
To prepare the fish, remove, skin and debone the fish.
Wash the fish in a colander and also remove any fat and remaining bones.
Squeeze out excess water by using your hands.
Now chop the fish into smaller pieces, then place them in a food processor.
Add egg white, sugar, salt, and mirin, and blend until you get a smooth fish paste.
Place half of the paste into a smaller bowl. Add several drops of pink food coloring and mix until the paste is pink or light red. Set aside.
Line your counter with plastic wrap and spread out the remaining white paste in a rectangle shape.
Now measure half an inch from the border of the white rectangle and then place the pink paste on top of the white one.
Using the plastic wrap, start rolling the fish cake into a log shape, making sure to roll tightly. The roll should be pretty thin.
Now put the fish cake roll into the steamer and let it steam for 15 minutes.
Once ready, let it cool. Then, remove the plastic wrap.
Use a knife with a serrated edge to cut the fish cake and give it those zig-zag edges.