1.Make spice paste; place lemongrass and coriander roots in mortar and crush to a paste with pestle. Add ground turmeric, ginger, cumin, palm sugar and fish sauce. Grind to combine.
2.Make sauce; heat vegetable oil in saucepan over medium-high heat. Fry paste for 2 mins until fragrant. Stir in onion and cook for 3 mins. Add coconut milk and fish stock; bring to a simmer.
3.Cook fish; gently lay fish into sauce and cover saucepan with lid. Reduce heat to medium and poach fish for 8 mins until nearly cooked. With 4 mins to go, add choy sum, re-cover pan and cook until tender.
4.To serve, garnish fish with coriander leaves and green onions. Serve with steamed rice and lime wedges.
This dish is great for those who love fragrant Asian flavours, but could do without the spicy heat. Equipment: Sharp knife; grater mortar and pestle; large wide-based saucepan with lid; spoon; ladle Barramundi: We used frozen as it cost $16.97 a kilo, but you can use fresh – about $33 a kilo -if you prefer