To make your roux, in a large cast-iron skillet, mix the flour and the oil or grease. Place in an oven set at 350°F and let it cook for 2 hours (or until your desired color), stirring every 20 minutes.
While the roux is cooking, make the chicken and broth. First, season the chicken parts with the salt, black pepper and Cayenne. Place the chicken parts in a large pot with the quartered onions, whole garlic, quartered celery, bay leaves. Cover with water. Bring to a boil then turn the heat down to low and simmer for 1 hour.
After an hour, remove the chicken from the pot. When cool enough to handle, remove the fat and pick the meat off the bones and cut into pieces. Meanwhile, when the broth is cool enough to handle, strain the broth, discarding the vegetables. You should have about 8 quarts.
Clean the pot, then add 1 tablespoon of canola oil. Add the diced onions, celery, and bell pepper, and while stirring occasionally, cook for 10 minutes or until fragrant. Throw in the minced garlic and cook for 30 more seconds. Now stir in the roux and cook it with the vegetables for 5 minutes, stirring every so often. Add the chicken meat and sausage and cook for 15 minutes, stirring occasionally. If things start to get sticky, pour in some water.
Slowly whisk in the strained chicken broth to the roux, vegetable, meat mixture. Throw in the bay leaves, thyme, and the Worcestershire, bring to a boil and then simmer for 1 hour. Fifteen minutes before it’s done, add the minced green onions and filé powder and check to see if it needs salt, black, and Cayenne pepper.
Remove the bay leaves and serve over cooked rice with file powder for people to add to their bowls.
Notes
Filé (pronounced fee-lay) powder is ground sassafras leaves. If your store doesn't carry it, it can be ordered for Cajun Grocer.