Commercial curry powder varies from brand to brand. Some are really potent while others are bland. How much you need to use depends on how spicy your curry powder is, and how spicy you want your salmon curry.Overcooking seafood is a bad idea. Fish flesh turns papery dry when exposed to heat for too long. Initially, cook the salmon cubes for a minute or so to let them absorb the flavors of the spice base and the fish sauce. Cook them for another minute or so after the coconut cream has been added. Bok choy is not a must here. But adding leafy vegetable to curry instead of the usual potatoes and carrots is surprisingly good. Feel free to use other greens such as spinach or kale.