A sachet d'épices (pronounced "sa-SHAY DAY-pees") is a small cheesecloth sack containing herbs and spices used to add flavor to stocks, soups and sauces. It translates literally to "bag of spices" in French.
Often referred to simply as a sachet, it's used in a similar manner to a bouquet garni, with the main difference being the fact that a sachet's ingredients are enclosed in cheesecloth while a bouquet garni's are not.
This means that spices such as whole peppercorns, and dried herbs, which couldn't be used in a bouquet garni, can go in a sachet.
Common items included in a sachet d'épices are:
These ingredients are tied inside a piece of cheesecloth, which is then suspended in the simmering liquid at the end of a length of cooking twine, and usually tied to the pot handle so that it can be easily retrieved.