Filé powder is a staple of Cajun cuisine, and a popular condiment at the table in much of the American South. It is especially important for gumbo, and is sometimes called gumbo filé, in a reference to the dish that it is most frequently used with. Typically, filé powder is sold alone as a solo spice, although it may be included in Cajun seasoning blends as well. Some markets carry it in the spice section, and it can also be ordered from producers in the South.
The origin of filé powder is the sassafras tree, a deciduous tree which is native to the Eastern United States. Sassafrass has light green leaves which can be simple to tri-lobed, and typically only new growth is harvested to make filé powder. When the fresh leaves are crushed, they emit a slightly lemony odor, and the dried leaves have a potent kick, imparting a savory earthy flavor to foods. The roots and bark of the tree were once used to make root beer, although a carcinogen present in these parts of the plant has led to a decline in their use.
After the fresh leaves are harvested, they are cleaned and hung to dry. Once the leaves are totally dry, they are usually crushed by hand and then powdered, either in a blender, a grinder, or a mortar and pestle. The resulting fine green filé powder is packaged in airtight container for sale or future use. As with other spices, filé powder does best when stored in a cool dry place and kept away from light. Whole dried sassafras leaves are also sometimes available.
Usually, filé powder is added at the very end of the cooking process. It works well as a thickener and seasoning, but it can also make a dish stringy and too thick. In some cases, filé powder is simply set out as a condiment, allowing diners to add as much as they please to their foods. It is lightly sprinkled on like pepper and then stirred in.
Both Cajun and Creole dishes may call for filé powder. For cooks in the South, the dried sassafras spice is a staple in cooking, as it forms an important part of the traditional Cajun flavor profile. As it stales, filé powder will lost potency, just like any other herb. For this reason, most cooks replace their filé powder annually, harvesting it themselves, if possible, so ensure that the powder is as fresh as possible.