The secret to whipping up a gumbo that makes your neighbors jealous is in Kisatchie National Forest. At least, that’s what John Oswald Colson and Dustin Fuqua might tell you. Every summer, Colson and Fuqua make their way through the longleaf pines of Central Louisiana until they find a wispy, unassuming tree with mitten-shaped leaves low enough to pick. This is the sassafras tree, and the highly coveted, gumbo-elevating herb made from its dried and pulverized leaves is called filé. Colson, who is officially recognized by the state government as…