Cut the fish into 2 8 oz. portions or 4 4 oz. portions as desired.
Lightly season the fish with salt on all sides.
Add lemongrass powder and toss well.
Heat the oil in a skillet.
Toss the fish in rice flour and shake off the excess flour.
Add the fish to the hot pan, skin side down.
Sear the fish on both sides, about 3 minutes on each side.
Remove fish to a paper towel lined plate.
Discard excess oil, leaving 1 tablespoon in the pan.
Add curry paste and fry on medium heat for about 5 minutes.
Add coconut milk. Whisk together and bring to a boil.
Reduce to a simmer and cook for 5 minutes on low heat.
Add fish and spoon the curry sauce over the fish. Cook until fish is cooked through, about 5 minutes.
Add mango and cook for another 2-3 minutes.