Mix all the ingredients for the Ponzu and Miso Butter Glaze in a sauce pan. Bring it to boil and remove from the heat immediately. Let cool.

In a plastic bag, marinate the steak for 1 hour with half of the glaze. Fire up the grill, scrape off the excess glaze and then grill. If the grill flares up, move the steak to the cooler spot to prevent burning. Return the steak to the heat when the flame dies down.

Grill each side of the flank steak for about 3-4 minutes, then gently pick it up with a pair of tongs and grill the other side for another 3-4 minutes, or until the surface becomes nicely charred or to your desired doneness. Brush some glaze on the surface of the meat and let set on the grill for another 1 minute on each side.

Remove the steak from the grill and let rest for 10 minutes. This will allow the juice inside the steak to redistribute so it will not leak out when you slice it. 

While the steak is resting, toss the fresh herb salad with ponzu.

On a serving plate, place about 1 tablespoon of the Ponzu and Miso Butter glaze on the plate. Place the steak on top of the glaze. Drizzle a little more glaze on top. Serve immediately with some fresh herb salad.