In a large pot, heat the vegetable oil over medium-high heat.
Add the flour and stir constantly to make a roux.
Cook until the roux turns the color of milk chocolate.
Immediately add the onions, celery, and green bell peppers.
Cook for about 5 minutes until the vegetables are softened.
Add the sliced andouille sausage to the pot and cook for 3-4 minutes.
Stir in the salt, cayenne pepper, and bay leaves.
Gradually add the chicken broth, stirring until the roux mixture and broth are well combined.
Bring the mixture to a boil, then reduce heat and simmer for about 45 minutes.
Add the cooked chicken, minced garlic, chopped okra, parsley, and green onions.
Cover and simmer for an additional 30 minutes.
Serve the gumbo hot with cooked rice on the side or mixed in.