We often make reference to letting a piece of meat “rest” once it’s finished cooking. At its simplest, resting simply means letting a piece of meat sit before cutting into it. Any chef will tell you it’s one of the most important steps in cooking meat, but why is it necessary?
When cooking meat, the muscle fibres of the meat contract, forcing out liquid from the spaces between. As the meat cools, the muscle fibres relax and reabsorb the juices within the meat. Cutting into meat directly out of the oven essentially spills these juices onto a cutting board, taking with it a great deal of the flavour and moisture of the meat.
Secondly, letting meat rest evens out the doneness of the meat as it continues to cook slightly, resulting in a more even temperature. The best way to let meat rest is to place it on a rack or place in a warm (but not hot) place, with a tented piece of vented foil placed over top of it to keep it warm while letting the steam escape.
For a small piece of meat, 5 – 10 minutes is often sufficient, whereas a larger cut like a roast chicken should rest for at least 10 – 15 minutes.