Peel the tsukune yam and cut it into 6–8 pieces. Place them in a thick plastic or storage bag and lightly mash with a rolling pin, leaving some texture.

Cut the nori sheet in half horizontally, then into 4 equal strips vertically.

Scoop 1/8 of the mashed yam mixture with a spoon and place it on a piece of nori. Fold the nori in half to wrap the yam. Repeat to make 8 pieces.

Heat butter in a frying pan over medium heat and arrange the wrapped yam pieces. Cook until browned, then flip, cover with a lid, and cook on low heat for 2 minutes.