Prep all the vegetables and set aside.
Heat a tablespoon of vegetable oil in a large skillet. Sauté the sliced andouille sausage until lightly browned then remove to a plate lined with paper towels to drain. Cover the plate and set aside to a warm location until needed.
Heat 3/4 cup vegetable oil in a large soup pot over medium-high heat until shimmering and almost smoking. Add the flour and cook, stirring constantly, until the roux is the color of a copper penny (not an old one!) Add the onions, celery and bell pepper and sauté for 10 minutes, stirring frequently to prevent burning. Add the minced garlic and sauté for a minute or two or until fragrant.
Add the tomatoes, parsley, thyme, red pepper flakes, and bay leaves. Cook for 10 minutes, stirring frequently, while slowly adding a small amount of chicken broth if needed, to prevent burning.
Add all the remaining chicken broth to the pot with the vegetables, and bring to a boil. Cover the pot and reduce the heat to low. Simmer for 30 minutes, stirring occasionally.
Add the shredded chicken, frozen okra and half the sausage to the soup pot. Cover and simmer for 1 hour, stirring occasionally.
Turn off the heat and add the remaining sausage, the filé gumbo powder and the shrimp (if using). Stir well, cover and rest for 30 minutes.
To serve, gently reheat if needed. Season with salt and pepper and remove the bay leaves.
Serve over hot cooked rice and garnish with fresh chopped parsley and green onions if desired. Serve with cayenne pepper or hot sauce for those that want a little more spice!