Place the Thai red curry paste, fish sauce, palm sugar, ground turmeric, coconut milk, chicken stock and fresh ginger in a medium saucepan and season with a generous pinch of salt. Whisk to combine.
Bring to a boil over medium-high heat, whisking to combine, then reduce the heat to low, cover and simmer for 15 minutes.
Add the cod fillets to the coconut broth, then cover and cook until the cod fillets are just cooked through, 5 to 8 minutes depending on their thickness. When done, the flesh will flake when gently pressed.
To serve, carefully transfer the cod fillets to a shallow serving bowl, then ladle the broth over the top. Finish with the fresh coriander and optional drizzle of chilli oil. I recommend serving this with rice (it soaks up all of that deliciously fragrant Thai curry broth), a side of steamed veg, and a few lime wedges for squeezing over.
