Milk

Milk looks simple. It is not. What you see in the glass is a suspension of fat, dissolved milk sugar and protein, held together in water. That is why it behaves the way it does when heated: a delicate skin forms on the surface, the protein tightens and can curdle if you rush it, the sugar caramelizes if it sits too long over a flame. Respect that, and milk rewards you.

Choose it by smell first, always. Fresh milk smells clean, faintly sweet, almost like grass and nothing else. Any sourness, any sharpness in the nose — put it back. Look at the color too: it should be even, opaque, never bluish or watery at the edges.

Some people say full-fat milk is heavy, that skimmed is the wiser choice for cooking. No! Fat carries flavor, and it gives the liquid a richer mouthfeel, keeping sauces wonderfully smooth. That is the whole reason a good sauce or a proper rice pudding needs real milk, not skimmed water with a memory of milk.

The mistake this belief leads to: cooks reach for skim milk in a sauce, then wonder why it splits, why it tastes thin, why the dish has no soul. Buy whole milk. One hundred grams gives you sixty kilocalories, over three grams of protein, over three of fat — that is not excess, that is structure.