Cut the fish into bite-sized chunks and set them into a bowl with the shrimp (or crawfish). Season with 1 tablespoon Cajun seasonings and refrigerate until ready to use.
Make a roux by heating the oil in a large pot or Dutch oven to medium heat. Add the flour and stir to form a slurry. Cook, stirring constantly to keep the roux from burning, for 20-30 minutes, or until the roux darkens to the color of chocolate.
Add the onion, peppers and celery. Cook, stirring often, for 5-6 minutes, or until the vegetables soften.
Stir in the garlic, thyme and bay leaves and cook for 1 minute.
Stir in the remaining Cajun seasonings, chopped tomatoes, seafood stock, hot sauce, and salt and pepper to taste. Reduce heat and simmer for 1 hour. Stir occasionally. You can simmer longer if you’d like to continue developing flavor.
Increase heat to medium and add the fish and shrimp. Cook for 10-15 minutes, or until the seafood cooks through, and the fish becomes flaky.
Remove from heat, sprinkle with parsley or green onion (or both), and red chili flakes. Serve.
