Creole gumbo recipes usually call for the addition of filé powder after the gumbo is cooked and the heat has just been turned off. The filé thickens and flavors the gumbo.
You can mail-order filé powder from Louisiana or find it in gourmet foodie shops – or you can make your own. I'm strongly partial to making my own, for several reasons. While premade filé from good sources can be perfectly legit, many store-bought versions are stale, off-color and even loaded with "filler" ingredients, like oregano, thyme and other garden-variety herbs.
(I can get those in my own garden, and I don't necessarily want them in my gumbo.)
Filé powder is the dried, powdered leaves of the sassafras tree. If you live in the Eastern U.S. or Canada, this native tree is very likely growing wild in your area, even in city parks. Once you've gathered the leaves from the tree, it takes them about a week to dry out enough to be turned into filé powder.
How to Make Your Own Filé Powder
Find some sassafras trees. Sassafras typically has three leaf shapes present on one tree: a simple oval, a three-lobed maple leaf shape, and a two-lobed mitten shape. Unlike mulberry trees, which can also have all three leaf shapes, sassafras leaves have smooth margins with no teeth. Another way to identify sassafras: every part of the tree smells like root beer when crushed.
Snip off the tips of a few branches with 5-10 leaves attached. Bundle these together with rubber bands and hang them in a dry place away from direct heat or light. They should be crispy dry within a week. Drying them in the sun can turn them brown and greatly diminish their flavor potency.
Strip the leaves from the branches. Process the leaves in a coffee or spice grinder until they become a green, aromatic powder. You can also grind the leaves with a mortar and pestle.
Sift the powder through a fine sieve, if desired, to remove pieces of stem and other bits. This can be time-consuming if the sieve is too fine; alternatively, you can simply pick out any pieces that won't dissolve in liquid.
Store the powder in a tightly covered glass jar away from direct light or heat.
Tips for Using Filé Powder
- Filé is more than a thickener; it also imparts an earthy flavor and has a fruity aroma similar to coriander seeds.
- Add filé to gumbo or other liquid mixtures shortly before serving. Adding it while the liquid is boiling can yield a stringy or slimy texture. For the same reason, if you're making the recipe well in advance of serving, don't add the filé during the initial cooking; wait until it's reheated (and you're ready to serve) before adding the filé.
- The bark of sassafras root contains about 2% essential oil, which is primarily composed of safrole, a carcinogen. Commercial formulas of sassafras products may have the safrole removed to meet FDA requirements.
- Many gumbo recipes use okra or a dark roux, rather than filé, as a thickening agent. If you simply can't get your hands on filé powder, consider a recipe that doesn't use it.