This spice crust gives the fish a wonderfully fragrant piquancy. To allow the spices to speak for themselves, I serve this dish without a sauce, just adding a couple of condiments instead. Salmon or trout from anywhere in the world may be used.
To make the spice crust, dry-roast chilli and whole spices except mustard and nigella seeds over gentle heat until fragrant and slightly coloured. Cool, then grind to a fine powder. Stir in mustard and nigella seeds, ground cassia and ginger, salt and chickpea flour.