In your heavy-bottomed pot over medium heat, cook sausage slices until browned on both sides. Remove with a slotted spoon and set aside.
In the same pot, cook you chicken thighs for a few minutes on each side. Remove, set aside, and once cooled chop into small pieces. (they will finish cooking in the gumbo). Be careful not to burn the bottom of the pan. Adjust the heat if you need to.
In the same pot, add oil (or butter) and flour. Stir constantly for 20–30 minutes until it reaches a deep, chocolate-brown color. Be patient — this is the flavor foundation.
Add chopped onion, bell pepper, jalapeño, and celery to the roux. Cook 5 minutes until softened, stirring often. Add minced garlic and whites of green onion and cook another 30 seconds.
Return sausage and chicken to the pot. Stir to coat everything in roux. Slowly pour in the chicken stock while stirring to prevent lumps.
Add bay leaves, thyme, hot sauce, salt, cayenne, and both Bayou City seasonings. Stir and bring to a gentle boil.
Reduce heat to medium-low. Cover partially and simmer for 45 minutes, stirring occasionally and skimming any fat from the surface.
Stir in gumbo file Simmer another 15–20 minutes.
remove from heat and stir in half the green onions, taste, and adjust seasoning. Serve hot over white rice or potato salad, garnished with remaining green onion.
