In a small bowl, combine the scallions, mustard, thyme, pepper and ginger. Rub the mixture evenly on both sides of the steak.
Put 2 of the papaya skin halves in a glass baking dish, flesh side up. Add the steak and top with the remaining 2 papaya skins, flesh side down; the skins should cover the surface of the meat. Cover and refrigerate for 1 to 1 1/2 hours.
Light the grill or preheat the broiler. Discard the papaya skins. Lightly oil both sides of the steak and season with salt. Grill or broil the steak, turning once, for about 10 minutes, or until medium rare. Thinly slice the steak across the grain on the diagonal and serve hot with Malay Onion Sambal.