I don't deny that chopping the fish into such tiny pieces seems perhaps against the express ethos (if I might put it that way) but there's no logic that can dissuade me. Besides, it really means that you hardly have to steep the fish in the acidy juices at all before it is "cooked" or rather denatured (yes, that is the term) by the lime. Not that that is my reason: I find that eating big chunks or raw fish, no matter if it is cured in some way by its acid bath, can spook people out and this dainty confetti somehow doesn't. I am mad for it, and truth to say, really love it with a big bowl of tortilla chips on the side, but for elegance often produce little toasts or tostadas instead. I get a slender French stick or ficelle loaf and cut into thin slices; 1 loaf should yield about 40 mini tostadas. Brush with a little oil and then burnish slightly in a 400 degree F oven for 10 minutes. Use whatever firm white fish is available to you; my Mexican sources speak of sierra but that's not an option for me, geographically. If I find black cod, sometimes called Chilean sea bass (and is neither cod nor bass) then I use that, otherwise monkfish.