1.Cook onion on a heated oiled barbecue flat plate until browned lightly. Sprinkle onion with sugar and vinegar. Turn constantly on barbecue until onion is caramelised. Transfer onion to small bowl and cover to keep warm.
2.Meanwhile, boil, steam or microwave potato until tender, drain. Combine in a large bowl with oil. Cook potato on heated oiled barbecue until browned lightly.
3.Meanwhile, cook liver on heated oiled barbecue until browned both sides and just cooked through. Serve liver with onion and potato.