Before you begin cooking, chop all vegetables as directed and measure out your spices. Peel and devein the shrimp, if not already done. Set aside.

In a heavy-bottomed Dutch oven or large pot, heat the vegetable oil over medium heat. Once hot, gradually whisk in the all-purpose flour. Continue to whisk constantly, or stir with a wooden spoon, making sure to scrape the bottom and sides of the pot. Cook the roux for 20-30 minutes, or until it reaches a rich, dark peanut butter or milk chocolate color. This requires patience and constant attention to prevent burning.

Once the roux is the desired color, immediately add the chopped yellow onion, celery, and green bell pepper (the 'holy trinity') to the pot. Stir well to coat the vegetables in the hot roux. Cook for 8-10 minutes, stirring occasionally, until the vegetables have softened. Add the minced garlic and cook for another 1-2 minutes until fragrant.

Stir in the undrained diced tomatoes, shrimp stock, bay leaves, dried thyme, Cajun or Creole seasoning, Worcestershire sauce, and hot sauce. Bring the mixture to a boil, then reduce the heat to low. Cover the pot and simmer for at least 45-60 minutes, stirring occasionally, to allow the flavors to meld and develop. The longer it simmers, the deeper the flavor will be.

Taste the gumbo and adjust salt and black pepper as needed. Uncover the pot, increase the heat to medium-low, and add the peeled and deveined shrimp. Cook for 3-5 minutes, or until the shrimp turn pink and opaque and are just cooked through. Be careful not to overcook the shrimp, as they can become tough.

Remove the bay leaves from the gumbo. If using filé powder, stir it in just before serving. Do not boil the gumbo after adding filé powder, as it can cause the gumbo to become stringy. Ladle the hot Creole Shrimp Gumbo over individual portions of cooked white rice. Garnish generously with fresh chopped parsley and sliced green onions.