Combine the ingredients for the marinade in a zip lock bag. Marinate for several hours or overnight.
Prepare barbecue. Drain marinade into a small saucepan and bring to boil. Mix the cornstarch and water and add to the marinade and cook until thickened.
Grill steak for about 5 minutes on each side for rare. Transfer steak to platter; let stand for 10 minutes.
Thinly slice across grain and pass marinade as sauce.