Stock is the cheapest upgrade available to a home cook

Treat the sections below as a sequence. With making stock, getting the early decisions right makes the later ones much easier.

The ingredients are free

Chicken carcasses, vegetable trimmings, parmesan rinds, mushroom stems and herb stalks all go in a bag in the freezer until there is enough. This converts the least valuable part of your shopping into the ingredient that most improves everyday cooking. It also means stock costs time and almost no money, which reverses the usual relationship in cooking.

The bag in the freezer is the whole system; without it, stock never gets made.

Temperature decides clarity

A bare simmer extracts flavour and gelatine gently and leaves the liquid clear. A rolling boil emulsifies fat and breaks up particles, producing a cloudy, slightly greasy result. Clarity is largely cosmetic, but the greasiness is not, and it is the reason boiled stock tastes heavier.

Skimming the grey foam during the first twenty minutes removes the proteins that would otherwise break apart and cloud everything, and after that stage there is very little left to skim.

Roast for depth, do not for freshness

Roasting bones and vegetables first produces a darker, deeper, sweeter stock suited to braises and gravies. An unroasted white stock is cleaner and better for lighter soups and risottos. These are two different ingredients rather than two qualities of one.

If you are short of time, a spoon of tomato purée or a splash of wine added to the roasting tray and scraped in with the bones contributes the same browned depth to the pot that fond contributes to a pan sauce.

What should not go in the bag

Brassicas — cabbage, broccoli and cauliflower stalks — turn sulphurous over a long simmer and will dominate everything else in the pot. Potato peel clouds the liquid with starch and beetroot colours the entire batch, both of which narrow what the finished stock can be used for. Anything already spoiling does not become acceptable by being boiled, and the freezer bag is for trimmings rather than for a second chance at something past its best.

Heavily salted or already seasoned scraps are the other exclusion, since a stock is usually reduced later and whatever went in gets concentrated along with it.

Time depends on what is in it

Vegetable stock is finished in under an hour and becomes worse with longer cooking as delicate aromatics degrade. Chicken benefits from a few hours; beef bones from considerably longer to extract collagen. Over-cooking vegetable stock is the most common error and produces a dull, slightly bitter liquid.

A pressure cooker compresses all of those times dramatically and gives a cloudier result, because the liquid inside is well above a simmer whatever the dial suggests.

Substitute freely; the method matters more than the shopping list.

Store it so you use it

Reducing stock before freezing saves space and produces a concentrate that reconstitutes. Freezing in ice cube trays or small containers means you can take fifty millilitres for a pan sauce without defrosting a litre. Stock frozen in a single large block is stock that will not be used on a Tuesday.

At the stove, chilling it first sets the fat into a disc on the surface that lifts off whole, which is far easier than skimming a warm pot and leaves you with a jar of fat worth roasting with.

The takeaway

Keep a bag in the freezer. That single habit is what makes stock happen.

Taste it before it leaves the pan. That is most of cooking.