As the saying goes, first you make a roux. In a large, heavy cast-iron pot combine the oil and flour over medium-low heat. Stirring slowly and constantly, make a roux the color of a pecan. (This will take about half an hour.) When the roux is ready, add the onions, bell peppers, garlic and parsley. (The vegetables will prevent the roux from browning any more.) Stir and cook until the vegetables are very soft, about 10 minutes. Add the tomatoes, half the sausage, and the gumbo crabs. Stir for a few minutes, then add about 2 1/2 quarts of water. Add the seasonings, bring the mixture to a boil, then reduce the heat to medium-low and simmer for half an hour. Add half the shrimp and the okra and simmer for an additional hour. Adjust seasonings. (At this point the soup can wait for you.) When ready to serve, return the mixture to a boil, add the remaining sausage and shrimp, and cook for about 12 minutes. Adjust seasonings again. Serve over rice in deep bowls.
Makes 6 to 8 servings