In a large cast-iron Dutch oven or similar deep heavy skillet, melt ½ cup butter. Whisk in flour. Cook stirring or whisking over low heat until mixture is a caramel-colored paste similar to peanut butter. About 20 minutes.
To the pot add the onion, celery, pepper and onions; stir until coated. Cook over medium heat until the vegetables begin to soften, around 5-8 minutes. Add minced garlic, cooking for 1 minute longer.
Next, add the stock, tomatoes, Worcestershire sauce, Cajun seasoning, salt, pepper,cayenne, bay leaves and thyme. Bring to a boil.
Reduce heat; cover and simmer for 30 minutes, stirring occasionally.
Uncover, discard bay leaf and thyme stems. Add crawfish, lemon juice, green onions and 2 tablespoons parsley. Add a few dashes of hot sauce. Cook uncovered over medium low for 10-15 minutes or just until crawfish is heated through. Whisk in reserved 2 tablespoon butter. Mix well. (Reserve a few green onions for garnishing)
Serve ladled over cooked white rice, with hot sauce and garnished with reserved parsley and green onions.
Please note: If you want to thicken the etouffee further at the end of cooking you can by using tomato paste 1 tablespoon at a time until desired thickness is reached.
Notes
Cajun style etouffee wouldn't typically include tomatoes. We love them in this dish and they're included. You can omit them and adapt with extra fish or shrimp stock, if desired.