Another South Indian fish curry, this one from Hyderabadi. It is a very satisfying dish to prepare and eat. I suspect the sour character of this dish, which can be attributed to the tamarind, is an acquired taste. To offset this, I like to add a smattering of dark brown sugar at the end, but the choice is yours. The peanut butter is an integral component. If you cannot obtain fresh curry leaves you may use Thai basil leaves or ordinary basil leaves, but the taste will be quite different. Serve with rice and simply cooked vegetables. Adapted from a Madhur Jaffrey recipe.