Ceviche

Acid instead of fire — one of the rare times you can watch food change right in the bowl.

Buy the fish from someone you trust and ask whether it's fit to eat raw: sea bass, bream or perch work, and properly frozen beats 'fresh' from an unknown source. Cut it into one-and-a-half-centimetre cubes and keep it cold until the last minute. Squeeze the limes by hand and not to the last drop — squeezed dry, the peel gives bitterness. Mix the juice with salt, thinly sliced red onion, chilli and coriander, pour it over the fish and time fifteen minutes: the edges turn white, the middle stays translucent, and that's correct. An hour in the juice turns it to rubber, so don't leave it 'to marinate properly'. Serve straight away with boiled sweet potato or corn, and do drink the leftover juice — it's called tiger's milk and it isn't decoration.

Where else do you assume out of habit that longer means better?