This is a recipe for a classic, dark brown, shrimp gumbo in true Louisiana Cajun country fashion. Serve over rice. Browning the chicken pieces in the oil used for the roux adds flavor to the dish. I use the cooked chicken for chicken salad. File is added off the heat to thicken the gumbo. If added while the gumbo is still cooking, it may become stringy and unpleasant. File is ground sassafras leaves. It is available in many supermarkets.