Water

Water has no taste of its own, and that's exactly why it changes everything it touches. Salt dissolves in it, starch swells in it, flour turns to dough only once water is worked in. Put a pot on high heat and watch it: a hard, rolling boil throws bubbles all the way up and rattles the lid, while a lazy simmer just shivers at the edges. Drop your pasta into the hard boil and give it a stir right away — watch it move, and if it ever settles or huddles at the bottom, stir again.

Choosing water is mostly about your nose. Smell it before you use it — good water smells of nothing at all. A faint whiff of chlorine from the tap is nothing to worry about. But if it smells metallic, or musty like a damp cellar, don't cook with it. If that smell keeps coming back cup after cup, get your water checked rather than hoping it'll pass.

Some people say hot tap water boils faster, so why not use it to save time? No. It gets there sooner, true, but hot water sits in a tank and picks up more from old pipes on its way to your cup. Cold water is the safer choice for cooking. That habit of reaching for the hot tap leads people to cook rice and soup, even make tea with it, never once comparing the two side by side — a taste test most kitchens skip, and shouldn't.