Heat a heavy-duty 12-inch skillet over medium-high heat until hot, 1 to 2 minutes. Add the andouille and cook, stirring occasionally with a wooden spoon, until well browned, 4 to 6 minutes. Transfer to a large bowl. Add 1/2 cup water to the skillet and immediately scrape the bottom with a wooden spoon to release any cooked-on bits. Reserve this liquid.

Heat the oil in a 7- to 8-quart Dutch oven over medium-high heat. Season the chicken pieces with salt and pepper and saute the chicken in two batches until golden brown on both sides, 3 to 4 minutes per side. Transfer to the bowl with the sausage.

Add the flour to the oil remaining in the Dutch oven and stir constantly with a wooden spoon or heatproof spatula over medium-high heat until the roux reaches the color of caramel, 4 to 8 minutes. Add the onion and stir until the roux deepens to a chocolate-brown, 1 to 3 minutes. Add the celery, bell pepper, and garlic and cook, stirring frequently, until slightly softened, 3 to 4 minutes. Stir in the chicken broth, 1 quart of water, the liquid reserved from the sausage pan, and the sausage, chicken, bay leaves, and thyme.

Bring to a boil and then reduce the heat and simmer uncovered until the chicken is falling off the bone, about 45 minutes. Transfer the chicken to a plate. If you like, skim the fat from the surface of the gumbo with a large shallow spoon.

When the chicken is cool enough to handle, discard the skin and bones, pull the chicken meat into bite-size pieces, and return the meat to the gumbo. Season to taste with salt and pepper if necessary (you may find that the sausage and broth provided enough seasoning).

Five minutes before serving, add the scallions and hot sauce to taste. Serve in large soup bowls over 1/4 cup cooked rice per serving. Sprinkle 1/2 to 1 teaspoon of the file powder on top of each bowl of gumbo and stir to thicken, or pass the file at the table for everyone to add to taste.

Make Ahead: Store gumbo in the refrigerator for up to three days and then reheat gently before serving. As with many stews and braises, gumbo tastes better the second day. You can also freeze it for up to eight months. Simply transfer to freezer-safe containers.