Often I don’t have room for one more container of stock in my freezer, so I make easy-to-store frozen concentrated stock cubes. As the stock boils, the water evaporates, concentrating the stock’s flavor and making what is called a demi-glace. (This technique of boiling to reduce the liquid is also a way to boost the flavor of an insipid stock–but only if there is no salt in it.) The wider the saucepan, the faster the liquid will evaporate, but it will still take at least 15 to 20 minutes. The saucepan must be deep enough to prevent the stock from boiling over. Watch the stock carefully toward the end of the cooking time, as it can boil up quite dramatically.
- Before starting, pour 1 1/2 cups water into the saucepan you plan to use. This will show you the quantity of the concentrated stock you’re aiming for. Discard the water.
- Pour the stock into the pan and bring to a boil. Continue to boil until it is reduced by about three-quarters, about 15 minutes. Pour the stock into a glass measuring cup to see if it has reduced to 1 1/2 cups. If not, return it to the saucepan and continue to boil to reduce it further. The stock will become syrupy and turn darker.
- Pour the reduction back into the measuring cup and add a good pinch of salt. Taste for seasoning and allow to cool slightly. Then pour the stock into ice cube trays and place in the refrigerator. (I usually end up with twenty-four cubes, each about 1 tablespoon.) When cold, the cubes will set like jelly and can be popped out of the trays and stored in bags in the freezer.
- These stock cubes are four times as strong as the original stock. You can use them to boost the flavor of soups and sauces. Or, to reconstitute them to use un place of stock, add 3 tablespoons water along with each cube.
If you reduce the stock too much, just add a little water.
The information and recipe, contained within, is excerpted from Bones by Jennifer McLagan and can be purchased here.