1.Shell and devein prawns, leaving tails intact. Combine prawns with beef, chicken, sauce, garlic and chilli in large bowl; stand 15 minutes.
2.Meanwhile, make dipping sauce. Stir ingredients in medium saucepan until sugar dissolves.
3.Discard mushroom stems; cut a cross in the top of caps.
4.Cook ingredients, except green onions, in batches, on heated oiled grill plate (or grill or barbecue) until vegetables are just tender, prawns and beef are cooked as you like and chicken is cooked through.
5.Serve with green onion and individual bowls of dipping sauce.
You could use rump or sirloin steak instead of the beef eye fillet.