Chop the vegetables: Place the celery, onion, green bell pepper, and garlic into the bowl of a food processor, and pulse until the vegetables are finely chopped. You can also use a sharp knife to finely chop. Set aside.
Make the roux: Heat the oil in a large, heavy saucepan. Add the flour and whisk quickly to dissolve the flour. Turn the stove down to medium-low and cook for about 30 minutes, constantly stirring until the roux becomes a dark caramel color.
Once you get to the desired color, toss in the onion, green onions, bell pepper, garlic, and celery. This immediately drops the temperature of the roux and prevent it from burning.
Bring the mixture to a simmer over medium heat, and cook until vegetables are tender—about 10 minutes.
Meanwhile, add the sausage to the skillet on medium-high heat and brown them on both sides. This will help to render some fat off the sausage. Remove from heat and set aside.
Season the chicken with 2 tsp of cajun seasoning and brown them in the same pan with the rendered oil (add more if needed) for about 4 minutes. Remove and set aside.
Deglaze the pan with the chicken and shrimp stock. Then add the stock to the simmering pot of veggies, add the cajun seasoning, bouillon powder, thyme, sausage, chicken, and bay leaves. Stir, and bring to a boil over medium-high heat. Once it comes to a rolling boil, reduce the heat to medium and leave to simmer for one hour.
Add the shrimps and okra and cook for another 5 to 6 minutes or until the shrimps become pink.
Stir in file powder, green onions, and chopped parsley. Remove and discard the bay leaves and adjust the seasoning if necessary.
Serve over white rice, pair with cornbread, french bread, garlic bread or biscuits. Enjoy!