A master stock is a stock which is repeatedly reused to poach or braise meats. It has its origins in Chinese cuisine and is typically used in Cantonese and Fujian cuisines. Foods poached or braised in the master stock are generally referred to as lou mei.
Once the base stock has been prepared, it is then used as a poaching or braising liquid for meat. Chicken is the most common meat that is cooked in a master stock, although squab, duck, quail, and pork are also often used. The defining characteristic of a master stock from other stocks is that after initial use, it is not discarded or turned into a soup or sauce. Instead, the broth is stored and reused in the future as a stock for more poachings. With each use, the poached meats and other ingredients absorb the stock's flavor while imparting their own back into the stock. In this way, over time, flavour accumulates in the stock, making it richer and more complex with each poaching, while subsequent poached meats absorb this flavor and likewise become more flavorful.
In Non-Chinese cultures
Japan
Many oden restaurants keep their broths as master stocks, straining them nightly to maintain their lightness and clarity even as their flavors grow in complexity.
Thailand
The Bangkok restaurant Wattana Panich has kept the broth for its beef stew and beef noodle soup as a master stock for over forty years since moving to its current location.
United States
Between August 2014 and April 2015, a New York restaurant created dishes from a master stock for over eight months. As part of the restaurant's social media presence, the stock was dubbed "Perpetual Stu" and had its own Twitter account, highlighting new ingredients as it developed.
Safety
After use, if the master stock will not be immediately reused, it is usually boiled, skimmed, strained and cooled quickly to kill any microorganisms in the stock. The growth of microbes in the stock can potentially spoil the flavour of the stock or pose a health risk. The stock is then refrigerated or frozen until required. Refrigerated stocks may be kept for up to three days, while frozen stocks may be kept for up to a month. If the stock is to be kept longer it must be boiled before being returned to storage. In theory, a master stock could be sustained indefinitely if due care is taken to ensure it does not spoil. Otafuku, an oden restaurant in Japan, has kept its broth simmering since 1945. There are claims of master stocks in China that are hundreds of years old, passed down through generations of cooks in this way.
