Marinate fillet in teriyaki, ginger and garlic for 1 hour. Remove fillet, pat dry then seal in a hot pan [leave rare]. Toss oil, onion and fish sauce through cooked, refreshed and reheated noodles. Arrange fillet on top. Serve with wasabi mayonnaise and soy sauce. For the wasabi mayonnaise, mix the mayo, wasabi paste and garlic together until smooth. Serves 4 as a starter