Pat dry your fish fillet, cut it into strips, and blend it in a food processor.
Add egg white, sugar, salt, cornstarch, onion powder, and mirin. Continue to blend until you have a smooth paste.
Scoop ¼ of the mixture into a bowl, add red food coloring, and stir to combine. This batch should be a light pink color.
Cover a cutting board with plastic wrap and spread a layer of the remaining white paste on the board.
Layer a strip of red paste on top of the white, and starting on the longest side, roll it into a log shape, cover it with plastic wrap, and steam for 25-30 minutes. Repeat this process with any remaining paste.
Remove your steamed rolls from the steamer and slice them into ¼"-½" thick pieces.
Serve over a bowl of ramen, and enjoy!
Video
Notes
Aim for a consistent thickness when spreading the fish paste on the plastic wrap. This ensures even cooking and a uniform texture throughout the narutomaki.
Roll the fish paste tightly to avoid any gaps or air bubbles. This helps create a better-looking spiral pattern and ensures the layers stick together during cooking.
Allow the narutomaki to cool completely before slicing. You can even refrigerate them for some time before cutting them. This helps obtain clean and well-defined slices without the risk of the roll falling apart.