Stock and broth

Why

Bones and meat go into cold water and are heated slowly, so the soluble proteins have time to leach into the water and coagulate on the surface as foam that can be skimmed off. When stock boils hard, the agitation breaks up the coagulated proteins and the rendered fat into tiny particles and disperses them through the liquid; the stock turns cloudy and greasy, whereas at a gentle simmer the scum and impurities sink to the bottom or stay on the surface. Body comes from bones, joints, skin and wings: their collagen turns into gelatin with long heating, which is why good stock sets to a jelly when chilled. Salt goes in only at the end, because stock evaporates as it cooks and is reduced further in sauces and risotto, so stock salted early easily ends up too salty. A big pot of hot stock cools slowly; how to chill it quickly is covered by the Cooling and storing leftovers card.

How to do it

• Cover bones and meat with cold water so they are submerged and bring it slowly to a boil.
• Before it boils, skim the foam off the surface with a slotted spoon.
• Then turn the heat down so the surface only trembles now and then, and let the stock simmer without boiling hard.
• For more body, add bones with joints, skin or wings; add vegetables only in the second half of cooking.
• Strain the stock, lift the fat off the surface or once it has set after chilling, and salt only for its next use.
• Divide a large batch into smaller shallow containers and refrigerate it within 2 hours of cooking.

If it goes wrong

Cloudy stock can be used as normal, it just won't be clear; muslin or a fine sieve catches the coarser sediment, but only clarifying with egg white gives a truly clear stock, and don't let it bubble next time. Chill greasy stock and lift off the set fat. Dilute oversalted stock with water or unsalted stock; in a soup, more vegetables or noodles help as well. Stock that doesn't set when chilled needed more collagen-rich bones, but it still tastes good.