Heat the ½ cup vegetable oil in a large Dutch oven or heavy-bottomed pot over medium heat. Once shimmering, whisk in the ½ cup all-purpose flour until smooth. Switch to a wooden spoon or heat-safe spatula.

Cook the roux, stirring constantly and scraping the bottom of the pot, for 25–35 minutes. You're aiming for a deep chocolate-brown color — like dark milk chocolate or a copper penny. Don't rush this step and don't walk away. If it smells burnt, reduce the heat.

Once the roux is dark and fragrant, immediately add the diced yellow onion, 1 green bell pepper, and 3 stalks celery. The vegetables will sizzle dramatically — this is normal. Stir vigorously to coat everything in the roux and stop the cooking. Cook, stirring frequently, for 6–8 minutes until the vegetables soften.

Add the minced garlic and cook for 1 more minute, stirring constantly, until fragrant.

Add the sliced andouille sausage to the pot and stir to combine. Cook for 3–4 minutes to lightly brown the sausage and render some of its fat into the base.

Add the 1 ½ lb boneless skinless chicken thighs, all of the spice blend ingredients (2 tsp Cajun seasoning, 1 tsp smoked paprika, 1 tsp dried thyme, 1 tsp dried oregano, ½ tsp black pepper, ¼ tsp cayenne pepper add more, 2 tsp kosher salt, 2 tsp Worcestershire sauce, and 2 pieces bay leaves), and stir well to coat everything evenly.

Pour in the 6 cups chicken broth low-sodium preferred and add the 1 can diced tomatoes with their juices. Stir well, scraping up any bits from the bottom of the pot. Bring to a boil over high heat, then reduce to a gentle simmer.

Simmer uncovered for 40–45 minutes, stirring occasionally, until the 1 ½ lb boneless skinless chicken thighs are very tender and the gumbo has thickened and deepened in flavor. Skim any excess fat or foam from the surface as needed.

Stir in the 1 ½ cups frozen okra sliced and cook for 10 minutes. The 1 ½ cups frozen okra sliced adds both flavor and natural thickening to the gumbo.

Add the 1 lb large shrimp peeled and deveined and stir to submerge. Cook for 3–5 minutes, just until the 1 lb large shrimp peeled and deveined are pink and cooked through. Do not overcook. Remove and discard the 2 pieces bay leaves. Taste and adjust 2 tsp kosher salt, ½ tsp black pepper, and ¼ tsp cayenne pepper add more as needed.

To serve, place a scoop of cooked 4 cups long-grain white rice in the center of a wide, shallow mixing bowl. Ladle the gumbo generously around and over the 4 cups long-grain white rice. Garnish with sliced green onions, fresh fresh parsley chopped, and a small pinch of filé powder for thickening and flavor if using. Serve immediately.