In a Dutch oven over medium heat, add 2 tablespoons oil and when hot, add chicken cubes; season with salt and pepper; sauté them until no longer pink, about 2 to 3 minutes. Using a slotted spoon, transfer to a bowl and set aside. Add sausage and cook until browned, about 3 minutes. Transfer to bowl with chicken cubes and set aside.
Add the remaining 4 tablespoons oil and butter; reduce heat to medium-low. When hot, add flour and whisk constantly until the roux turns deep brown similar to chocolate color, about 20 to 30 minutes. Remove the Dutch oven from the heat to cool off, about 5 minutes.
Return pot to the burner and increase the heat to medium. Add onion and celery; sauté for 1 ½ minutes. Add peppers and sauté for 1 ½ minutes before adding garlic; sauté for 1 minute.
Return the chicken and sausage to the Dutch oven. Add diced tomatoes and stir to combine. Pour in chicken broth and season with thyme, creole seasoning, smoked paprika, hot sauce, Worcestershire sauce, raw sugar and bay leaves; stir well scraping the bottom of the pot to dislodge any brown bits. Bring to a boil, reduce the heat to medium and simmer for 45 minutes.
Add file powder, shrimp and green onions; stir well and cook until no longer pink, about 2 minutes. Taste and adjust seasoning if needed.
When serving, place a generous scoop of cooked rice in a bowl, spoon in gumbo and sprinkle on some chopped parsley. Serves 8.