Heat the oil in a saucepan over medium heat.
Add the curry paste and ginger.
Cook for 1 minute, then pour in the coconut milk and stir until it starts to boil. Let it boil until the sauce has reduced by half.
Add the fish stock, fish sauce, sugar, and lime juice.

Reduce the heat to a simmer.
Add the cod and poach for 3 to 4 minutes, or until it’s just cooked. Remove the fillets to four soup bowls and keep them warm.

Bring the liquid to a boil and cook for 2 minutes.
Add the peas, carrots, and basil, and cook for another minute.
Check the seasoning, and add salt, pepper, or lime juice as needed.
Pour the sauce around the fillets and garnish with coriander.