Preheat a grill pan or indoor/outdoor grill to high.
Combine ginger, tamari, lime juice, oil and grill seasoning in a large sealable plastic bag. Add meat to marinade and coat evenly. Let stand 10 minutes then grill meat 6 to 7 minutes on each side.
Place potatoes in a pot and cover with water. Bring to a boil, salt the potatoes and cook until tender, 10 to 12 minutes. Drain potatoes and add them back to the hot pot. Smash the potatoes with a masher to desired consistency with the cream and wasabi. Adjust salt, to taste.
While potatoes and meat cook, finely chop the scallions together with cilantro and lime zest.
Let meat rest 5 minutes then thinly slice on an angle against the grain. Serve meat on mash potato mounds with a garnish with a generous sprinkling of the chopped scallion-cilantro-lime zest.