Heat oil in a heavy pot over medium heat. Add diced onion, minced garlic, grated ginger, bruised lemongrass, and sliced green chili. Sauté until the onion is translucent and fragrant, about 4-5 minutes.

Bloom curry paste

Stir in the red curry paste and cook for 1-2 minutes, until it darkens slightly and the aroma blooms.

Add liquids and seasonings

Pour in coconut milk and fish stock. Add lime juice, fish sauce, and brown sugar. Bring to a gentle simmer.

Cook white fish

Add the white fish chunks to the simmering curry. Simmer gently for 4-6 minutes, or until the fish is just opaque.

Cook shrimp

Add shrimp to the curry and cook for 2-3 minutes, until pink and curled. Avoid overcooking.

Finish and season

Taste the curry and adjust salt as needed. Remove lemongrass if preferred. Stir in chopped cilantro just before serving.

Serve

Ladle the seafood curry into bowls and serve with steamed jasmine rice or crusty bread. Garnish with extra cilantro if desired.