How do I concentrate and freeze stock so it takes up less room?

The reason homemade stock so often ends up thrown away is that four litres of it will not fit in a domestic freezer. Reducing it first solves the storage problem and improves the stock at the same time, because a concentrated stock gives a sauce body that a diluted one cannot. The only rule is that it must be unsalted before you start.

What you'll need

• Strained unsalted stock
• Wide pan
• Ice-cube trays or small containers
• Freezer bags (optional)

Step by step

1. Strain and chill the stock, then lift off the fat.Fat does not reduce and it goes rancid in the freezer more quickly than the stock does. Once cold, it comes off the surface as a disc. Keep it if it is chicken or duck fat — both are excellent for roast potatoes.
2. Confirm it is unsalted before you reduce anything.Reduction concentrates salt exactly as it concentrates flavour. A stock that tastes correctly seasoned will be inedible at a quarter of its volume. If you have used a salted stock, reduce it only by half at most.
3. Boil it hard in the widest pan you have.Surface area governs the speed of evaporation, so a wide sauté pan reduces far faster than a stockpot. Boiling is fine at this stage — clarity no longer matters once the stock has been strained.
4. Take it to a quarter of its volume for everyday use.Four litres down to one. Diluted one to four this is back to normal strength. Taste it at this point: it should be intensely savoury, not bitter. Bitterness means it has caught on the base.
5. Or take it further, to a syrup, for a glace.Reduced to about a twentieth it becomes a dark, glossy syrup that sets to a firm rubbery block when cold. A teaspoon dissolved into a pan sauce gives instant body and depth. This is the most freezer-efficient form of all.
6. Cool it quickly and freeze in usable portions.Stand the pan in a sink of cold water to cool fast, then refrigerate. Freeze in ice-cube trays, pop the cubes out when solid and bag them. Label the bag with the strength — a cube of quarter-strength concentrate and a cube of glace are very different things.
7. Use from frozen.Cubes go straight into a hot pan. There is no need to thaw. Two cubes plus water makes a mug of stock; one cube dropped into a pan sauce at the end adds body.

Tips

• Flat freezer bags laid on a tray until solid stack like books and thaw in minutes. Better than tubs if you have more freezer than you have trays.
• Silicone ice-cube trays release frozen stock far more easily than rigid plastic. A tray with 30ml compartments is the most useful size.
• Reduce it in a stainless or heavy pan and stir the base occasionally as it gets syrupy. A scorched glace tastes bitter and is not recoverable.
• Frozen stock keeps well for six months and is still safe well beyond that; the flavour dulls rather than spoiling.
• A block of glace and a splash of water is a better emergency stock than any cube in the cupboard, and it costs nothing but the freezer space.

Keeping on top of it

• Turn accumulated bones and trimmings into stock (Whenever the freezer bag is full)
• Rotate frozen stock and use the oldest first (Every few months)

Questions people ask