Combine teriyaki sauce, rice vinegar, sesame oil and seed in a bowl. Divide into 2 bowls. Reserve 1 bowl for dipping.

To prepare the beef, slice beef flank steak thinly into strips with a sharp knife. Arrange beef slices on a plastic wrap, then cover with another plastic wrap and pound with meat pounder until 3mm thick.

Toss scallion and mizuna leaves with canola oil, salt and pepper. Leave aside to cool.

Place the vegetables across at 1 end of the beef. Roll the beef and tie with blanched scallion.

Heat a grill pan on high heat and brush with oil lightly.

Grill the rolls for about 5 minutes. Pour one bowl of sauce into the pan and coat the beef rolls evenly.