Peel and dice 2-3 starchy potatoes into roughly 1-inch cubes and place them in a large pot filled with cold water with a pinch of salt. Bring to a boil and cook for about 15 minutes until fork-tender.

Drain the cooked potatoes using a colander and let them sit for a minute to steam off excess moisture.

Mash the drained potatoes until completely smooth and free of lumps.

Incorporate 1 cup of potato starch, 2 tablespoons of vegan butter, and a pinch of salt into mashed potatoes and stir until combined into a cohesive dough.

Shape about ¼ cup of the potato mixture into a ball and flatten it into a disc about ½ inch thick. Continue shaping the remaining dough.

In a large frying pan, heat about ½ inch of cooking oil over medium heat and test readiness by dropping in a small piece of potato mixture.

Fry the potato mochi for 3-4 minutes on each side until golden-brown and crispy.

While frying, mix together ¼ cup soy sauce, 2 tablespoons brown sugar, and 2 tablespoons mirin over low heat until the sugar dissolves.

Once fried, drain mochi on paper towels, dip in the sauce, and wrap with a piece of nori, then serve warm.