carcasses or all of the above, substituting ham hocks, chicken backs, or necks, or other meats depending on availability. (For the 4 litre of stock you will need about 4 pounds of shells, bones and meat.) Bring to a boil, lower heat and simmer several hours. Strain the stock, discarding solids. (If time is a factor, simmer shrimp heads and shells and ham hocks in chicken stock for at least an hour.) 2) Cook okra in the oil in a large, heavy pot over medium heat, stirring and scraping until some of the sliminess is gone; about 15 minutes. Add tomatoes, onions, celery, garlic, peppers, vinegar, the seasoning and herb mix and cook over low to medium heat for about half hour, stirring and scraping often. 3) Blend the roux into the okra and tomato mixture. Very slowly blend the stock into the mixture. Simmer about 1 hour. 4) Add crab and shrimp and simmer 10 to 15 minutes. Add oysters and simmer about 5 minutes. Add green onions. Serve over rice with file` powder added to taste at the table. (File` powder should not be cooked.)