Combine oil and flour in large cast iron dutch oven over medium heat. Stirring constantly for 25 to 30 minutes, make a dark brown roux.
Add the onions, celery, and bell peppers and continue to stir for 4 to 5 minutes. Add the sausage, salt, cayenne, and bay leaves. Stir for 3 to 4 minutes. Add the broth. Stir until the roux mixture and water are well combined. Bring to a boil, then reduce heat to medium-low. Cook, uncovered, stirring occasionally, for 1 hour.
Add turkey to pot and simmer for 2 hours. Skim any fat on surface.
Remove from heat and stir in parsley, green onions, and filé powder. Remove bay leaves and serve. Yield: 4 (huge) servings
Notes: Original recipe used chicken andouille, chicken broth, and chicken rubbed with a spice mixture, but using turkey andouille, turkey broth, and turkey smoked with pecan wood sends this over the top.
Source: Television Food Network Episode #EM0309
Original recipe at food.com