Cook the potatoes
Peel and chop the potatoes into small, even-sized pieces.
Add them to a pot of boiling water and cook for around 10 minutes, or until a fork can easily pierce through them.
Drain well.
Make the mochi dough
Transfer the potatoes to a bowl and mash until completely smooth.
Add the salt, then gradually add the potato starch, mixing as you go.
Keep adding the starch a little at a time until you have a smooth, non-sticky dough that holds together.
You may need slightly more or less starch depending on how much moisture is in your potatoes, so don't dump it all in at once!
Make the sauce
Add the soy sauce, sugar and mirin to a small saucepan.
Bring to a boil, then reduce the heat slightly.
Mix the potato starch and water together to make a slurry.
Slowly pour the slurry into the sauce while continuously stirring until it thickens to a glossy, syrupy consistency.
Set aside.
Stuff the mochi
Take around 1 tbsp of potato dough and flatten it in your palm.
Add some shredded mozzarella to the centre, then cover with another small piece of dough.
Seal the edges well so the cheese doesn't escape while cooking.
Roll gently between your palms to form a ball, then flatten the edges to create a little square shape.
Repeat with the remaining dough. I made 9 pieces.
Pan fry
Heat around 1 tbsp neutral oil in a pan over medium heat.
Add the potato mochi and pan fry on both sides until golden brown and crispy.
Don't rush this step, you want a nice crust on the outside.
Glaze the mochi
Once browned, place two potato mochi onto each bamboo skewer.
Return the skewers to the same pan and pour over the sauce, or spoon the sauce directly over each piece.
Flip the skewers and continue cooking, spooning and basting the sauce over the mochi until they're deeply browned, glossy and glazed.
Finish
Place a small square of nori onto each potato mochi.
And that's it! You've officially made Zenitsu's potato mochi!