Tumeric and coconut poached barramundi

Ingredients

• 2 lemongrass stalks, outer layers removed, trimmed and sliced finely
• 3 coriander stalks, roots trimmed and leaves separated
• 2 teaspoons ground turmeric
• 2 teaspoons ground ginger
• 1/2 teaspoon ground cumin
• 3 teaspoons grated palm sugar
• 2 tablespoons fish sauce
• 2 tablespoons vegetable oil
• 1 brown onion, chopped finely
• 1 cup coconut milk
• 1 cup fish stock
• 4 180 g frozen barramundi fillets, thawed
• 1 bunch choy sum, trimmed and cut into 10 cm lengths
• 2 green onions (shallots), sliced
• steamed rice and lime wedges, to serve