Clean and wash the carrots and leek. Cut the carrots into thin sticks and the leek into thin rings.
Wash the fish fillets, pat dry, and cut into large cubes. Mix the flour and salt in a shallow bowl, then coat the fish pieces in the mixture.
Roughly chop the cashew nuts. Heat a wok or large pan over high heat. Add the cashew nuts and toast for 2-3 minutes, stirring often, until golden brown. Remove to a plate.
Add 2 tablespoons of oil to the wok over high heat. Fry the fish for 3-4 minutes on all sides until golden. Remove to a plate.
Heat 1 tablespoon of oil in the wok over medium heat. Add the carrots and leek, cook for 2 minutes, stirring occasionally.
Add the curry and stir for 1 minute. Stir in the coconut milk and vegetable stock. Bring to a boil, then reduce heat to medium-low and simmer for 4-5 minutes.
Return the fish to the sauce and simmer for 2-3 minutes until heated through and the fish flakes easily with a fork.
Transfer to serving bowls, sprinkle the roasted cashew nuts on top, and serve with rice.