Cut the potatoes into small pieces and soak them in water. Drain and place them in a microwave-safe container. Cover loosely with plastic wrap and microwave at 600W for 5 minutes. Mash the potatoes while hot and mix with mayonnaise, salt, and pepper.

Mash the hanpen in its bag by hand. Cut the bacon into 1cm wide strips.

In a bowl, mix the mashed potatoes, hanpen, bacon, and potato starch. Divide into 7 portions and shape into oval patties.