Heat ½ tablespoon oil in large pot over medium-high heat. Add sliced sausage and cook for 4-5 minutes or until crispy. Transfer sausage to a paper towel lined plate and set aside.

In same pot, heat remaining oil and butter over medium-high heat, until melted. Whisk in flour, to form a roux, and continue to stir constantly with a whisk or wooden spoon until roux turns a deep, chocolate brown color, about 10-15 minutes.

Once roux has reached desired shade, stir in onions, bell pepper and celery. Cook, stirring constantly, for 3 minutes, or until the vegetables release their steam. 

In crease heat to high and push vegetables to the side of the pan. Whisking constantly, stir in the turkey broth, to deglaze the pan. Continue whisking until all the flour is dissolved and the brown bits come off the bottom of the pan; about 3-5 minutes.

Add salt, pepper, creole seasoning, cayenne, bay leaves, turkey and reserved sausage to the pot. Reduce heat and simmer, uncovered, for 60-90 minutes, stirring occasionally to prevent burning. 

Skim off any fat that rises to the surface of the gumbo. Adjust seasonings and thin out with more stock if necessary. 

To serve, place mound of rice in bottom of bowl, ladle gumbo over and top with chopped parsley, green onions and 1/2 teaspoon filé powder, if desired.