Mince the onion and microwave in a heatproof container at 600W for 1 minute.

Cut the potatoes into bite-sized pieces, soak in water for 5 minutes, then drain. Microwave in a heatproof container covered with plastic wrap at 600W for 6 minutes.

Mash the potatoes in a bowl, add salt, pepper, and milk, and mix well.

Add the minced onion and corned beef to the potato mixture and mix. Shape into balls.

In a container, beat the egg, add flour and water, and mix until smooth.

Coat the potato balls in the egg mixture, then cover with breadcrumbs.