Method

1. Heat a barbecue grill to high. Rub salt and pepper on each side of steak, then spray with oil. Add to grill and cook for 2 minutes on each side or until medium-rare, then put on resting rack for 5 minutes.
2. Meanwhile, heat a wok burner or barbecue grill to medium. Put stock and cornflour in a small bowl, then stir to combine. Set aside.
3. Put oil in a medium frying pan and add to burner or grill. Add onion, chilli, lemongrass, garlic, ginger and coriander and cook for 2 minutes or until aromatic. Add pineapple, vinegar and fish sauce and cook for 1 minute. Pour in stock mixture and simmer until thickened.
4. Heat a barbecue grill to high. Spray oil on each side of prawns and scallops. Add prawns to grill and cook for 2 minutes on each side or until just firm. Add scallops and cook for 10 seconds on each side or until rare.

5. Put steak on plates, top with seafood and add sauce. Serve with bok choy.