Preheat the oven to 350 degrees F. Place flour in a baking pan and bake, watching and stirring occasionally until flour is a nutty brown color. Sift to remove the lumps of flour.
Saute chicken in oil in a large pot. Add sausage and cook until it begins to change color. Add onions, bell pepper and garlic and let cook until onion is clear. Add crabs and let cook until the crabs have changed color. Add thyme, cayenne, celery, bay leaves, green onions and flour and let mixture cook 5 minutes. Add stock and season with salt, pepper and Cajun seasoning. Cook for 45 minutes over medium heat, then stir in parsley. Serve over rice. Add gumbo file to each serving.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.