This is an old family recipe that has served well for many years. It uses a traditional dark brown roux and Gumbo File to thicken and flavor. Its high quality depends on the freshest seafood ingredients, although much time can be saved with prepared seafood and fish stock.
In a large cast iron skillet or heavy saute pan, add the oil. Heat the oil on high heat until the pan is smoking hot, then carefully whisk in the flour and reduce the heat to medium. Stir constantly throughout cooking to prevent scorching. Cook 30-45 minutes, or until a dark brown color and nutty aroma develops. Remove from heat for a few minutes before adding the garlic to prevent burning.
Fry garlic in this roux. Add onions and cook 10 minutes. Add celery, bell pepper, black pepper, salt, Old Bay, Italian herbs, Tabasco sauce, and Worcestershire sauce. Cook until vegetables are tender.
Add vegetable mixture to a 12-quart stock pot over medium-high heat, then add three quarts fish stock (see recipe below). Allow the liquid to come to a boil and simmer while preparing the shrimp, crab and oysters/steamers.
Precook shrimp in just enough water to cover, with 2 cubes Knorr fish bouillon and 1-½ teaspoons Old Bay seasoning. Drain, cool and peel the shrimp. Again, using the fish bouillon and Old Bay, bring the oysters to a boil in water until they just curl. Drain and cool. If using steamers (clams) instead of oysters, using the same procedure and seasonings, steam the clams, then shuck and clean before adding to the final boil.
After cleaning the lump crab for any odd shell fragments, add to stock pot and cook for ten minutes. Add parsley and chopped green onion and cook for another 10 minutes. Add the precooked shrimp, oysters/clams and cook for 5 minutes to heat through. At the very last add the file gumbo, blend well and remove from the heat and allow it to thicken.
Allow the gumbo to set and when reheating, simmer gently and serve with cooked rice if desired.
To make fish stock: Cook down about 2 pounds of fish scraps to make a simple fish stock. You can also add shellfish scraps for extra flavor. Place in small stockpot and add just enough water to cover. Add salt to taste, and simmer for 20-30 minutes. Strain the stock before using.