This is not a recipe.
Ceviche is not a recipe, it's a concept: seafood marinated in citrus juice. As simple as that, and as versatile as it gets. In Peru where ceviche originates, the idea is to use whatever is the catch of the day, with the fish varying according to what was available, and then marinated in citrus juice when the acid from the juice denatures the proteins in pretty much the same way cooking would.
This time, I went for sea bass, but any white firm fish would do - nothing that would dissolve in the lime juice or just break apart - think lemon sole, sea bream, tilapia or even scallops. It goes without saying that it has to be as fresh as possible so go to a fishmonger you trust. Ask them to fillet it for you, or if you're feeling adventurous buy it whole and fillet it at home like I did.
Once filleted, you can either cut up the fish in cubes or slice it thinly. Even top chefs disagree about this but I'll tell you what - if you prefer it to be thoroughly 'cooked', go with thin slices. If you want to go for a bit of a contrast between a 'cooked' exterior and a close to raw interior, go for the cubes. See? Versatile.
Concerning the marinade, you could experiment with anything from lime and lemon to grapefruit and orange. Jamie Oliver also recommends Japanese yuzu! In this case I went for half a pink grapefruit and the juice of one lime. Obviously, depending on your amount of fish you adjust the amount of juice accordingly.
Now, the spices. I used chilli (half of it to be precise), but again, sky's the limit. You could add ginger, finely sliced red onion, coriander, whatever tickles your fancy. Add everything to a bowl or a tupperware container, season with salt, give it a good stir and let sit in the fridge for fifteen minutes.
After the fifteen minutes have passed, take it out, give it another good stir and check the fish. It should have turned opaque and somewhat firmer. If you like what you see, the ceviche is pretty much ready. However, I couldn't just serve such a pretty sight without a few more touches.
I added some of the pulp from the grapefruit and decided I also wanted to serve it on a bed of avocado ribbons. To do this, just take a peeler, and start peeling away the flat side of the avocado, until you have a happy little pile of thin avocado ribbons.
However, to avoid mushiness (technical term), you could peel the avocado directly onto the serving plate. Alternatively, you could just cut it into little cubes and stir it into the fish - I did both.
If you're not into my avocado creation, your fridge is your oyster. You could go to town with fruit like pomegranate seeds, grapefruit pieces and passion fruit pulp or herbs like mint, parsley or coriander. Anything which would complement the fresh and zingy ceviche will do.
Go on, impress a date.