Heat the vegetable oil in the large pot or Dutch oven over medium heat. Add the flour and stir continuously to make a roux. Continue stirring until the roux turns a rich, dark brown color, resembling melted chocolate. This step may take about 15-20 minutes, so be patient and attentive to prevent burning.
Once the roux is ready, add the diced onions, bell peppers, celery, and minced garlic to the pot. Sauté the vegetables for about 5 minutes until they become tender and fragrant.
Add the sliced sausage to the pot and cook for an additional 5 minutes, allowing the flavors to meld.
Pour in the diced tomatoes along with their juice and stir well. Add the chicken broth, dried thyme, paprika, cayenne pepper, bay leaves, salt, and black pepper. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and let the gumbo simmer for 20 minutes, stirring occasionally to prevent sticking.
After 20 minutes, add the bite-sized chicken pieces and sliced okra to the pot. Simmer for another 15-20 minutes or until the chicken is fully cooked and tender.
Taste the gumbo and adjust the seasoning as needed, adding more salt or cayenne pepper if desired.
Once the gumbo is ready, remove the bay leaves and discard them.
Serve the Chicken and Sausage Gumbo over a bed of fluffy white rice. Garnish with fresh chopped parsley to add a burst of color and freshness.