Peel and cut the potatoes into bite-sized pieces. Soak them in water for 5 minutes. Place them in a microwave-safe container, cover loosely with plastic wrap, and microwave at 600W for about 6 minutes.

Mince the onion and place it in a microwave-safe container. Add butter on top, cover loosely with plastic wrap, and microwave at 600W for about 2 minutes.

Make a slit in the tarako skin and extract the contents.

Mash the cooked potatoes while warm and place them in a bowl. Add the cooked onion, mayonnaise, tarako, and salt and pepper. Mix well and divide into 12 portions, shaping each into a ball.

Coat each ball in flour, then beaten egg, and finally breadcrumbs.