In a large skillet, over moderate heat, melt 3 tablespoons of the oil. Add the okra and, stirring constantly, cook until the white threads disappear. Transfer to a plate and reserve.

Add the remaining 3 tablespoons of oil to the skillet and heat over medium heat. Season the chicken with the salt and pepper then sear to a golden brown on both sides, about 8-10 minutes. Use tongs to transfer the chicken to a paper towel-lined plate as they cook. When the chicken pieces are cool enough to handle cut them into pieces and reserve.

In a 6-quart Dutch oven or large pot set over medium-high, melt the butter, gradually add the flour. Stirring constantly, cook the roux until it becomes caramel colored, being careful that it does not burn.

Add the onions, celery, red and green bell pepper, garlic, cayenne, if using, basil, thyme, oregano and Creole seasoning, cook for 3 minutes. Gradually add the chicken broth, stirring constantly to prevent lumps. Add the sliced andouille sausage and the reserved chicken. Stir in the tomatoes, reserved okra, bay leaves, Worcestershire sauce and the thyme sprigs. Bring the mixture to a boil, reduce the heat to low and simmer, uncovered for 30 minutes.

Remove from the heat, adjust the consistency to your preference by either adding additional chicken broth for a thinner sauce or allowing to reduce further for a thicker sauce.

To serve: Remove and discard the bay leave and the remains of the thyme sprig. Ladle the gumbo into soup plates. Serve a small dish of file powder for guests to sprinkle on their serving if desired. Serve with white rice and garnish with chopped parsley.