Preheat the oven to 180°C (160°C fan, gas 4). Salt the duck breast fillets and slash the skin in a diamond-shape pattern.
Heat a non-stick pan, add the duck breast fillets, skin side down, and fry for 4-5 minutes until the skin is golden. Turn and fry on the other side for 1-2 minutes. Place in an ovenproof dish and cook in the oven for 12-15 minutes until cooked through.
Crush the lemon grass roughly.
Cut the garlic into fine slices.
Place the duck roasting juices and soy sauce in a pan and heat through. Pour in the coconut milk. Add the lemongrass and sugar. Heat through then leave to stand for 10 minutes.
Meanwhile, peel the pineapple and dice the flesh.
Wash, deseed and dice the peppers.
Wash and quarter the aubergines.
Add the curry paste, light soy sauce, ginger, garlic and curry leaves to the coconut milk. Add the aubergines and peppers and simmer for 5-8 minutes. Add the pineapple and season with lime juice. Remove the lemongrass. Cut the cooked duck into thin slices and place on the curry. Serve sprinkled with some chilli salt.