Heat the oil in a large dutch oven pot, over medium heat, for about 5 minutes so it gets very hot. Add the flour and whisk, forming a roux.
Lower the heat to medium low and cook, stirring constantly, until the roux becomes dark like chocolate, about 30 to 45 minutes. Be careful not to burn it or you'd have to start again!
Add the onions, garlic, bell peppers and celery and stir to combine. Cook for a couple of minutes until softened.
Add the beer, chicken broth, bay leaves, dried spices, Worcestershire sauce, cayenne pepper and salt. Bring to a boil, stirring occasionally, and then reduce to a simmer. Add the sausage and stir to combine. Cook for 1 to 2 hours, stirring every now and then, and skimming off the fat that rises to the surface.
Add the turkey and cook for 15 more minutes, just to warm it up.
Taste for seasoning and fix salt if needed.
Garnish with parsley and/or green onions.
Serve immediately, with rice, or keep it in the fridge overnight for the flavors to develop even more!