１Boil the Chinese cabbage and spread it over a zaru, a flat basket made of bamboo. After the cabbage cools, squeeze dry and cut into 10cm-long squares. Sprinkle it with soy sauce. ２Lightly toast both sides of the nori. Spread the Chinese cabbage over the nori and thinly spread mustard over the cabbage. Roll from the side closest to you. ３Cut 2 into bite-sized rolls and serve.