Peel and chop the potatoes into bite-sized pieces. Place them in a microwave-safe container, add 1 tbsp of water, cover loosely with plastic wrap, and microwave at 600W for about 5 minutes until soft.

Mash the hot potatoes with a fork, then mix in the potato starch, milk, and salt until smooth. Divide the mixture into 8 portions.

Flatten one portion of the potato mixture in your hand, place 1/8 of the shredded cheese in the center, and fold the dough around the cheese to form a 1cm thick circular patty. Repeat for all portions.

Heat butter in a frying pan over low heat until partially melted. Place the potato mochi in the pan and cook for about 2 minutes on each side until golden brown.