Ingredients

Makes about 20 cups, serving 10 to 12 as a main course

　　

For shellfish stock

shells from 1 1/2 pounds small shrimp

　　2 pounds frozen Alaskan King crab legs (about 4 legs), rinsed and broken into large pieces at joints of necessary

　　5 quarts water

　　1 onion, halved

　　1 carrot, halved

　　1 teaspoon whole black peppercorns

　　1 bay leaf

　　2 fresh parsley sprigs

　　1 1/2 teaspoons salt

　　1/3 cup vegetable oil

　　1/2 cup bread flour

　　2 large onions, chopped

　　1 green bell pepper, chopped

　　2 celery ribs, chopped

　　1 1/2 pounds small shrimp, shelled

　　1/2 pound lump crab meat, picked over

　　2 dozen oysters, shucked, reserving their liquid

　　1 cup thinly sliced scallion greens (about 1 bunch)

　　Accompaniment: Cajun-style White Rice

　　

Make stock:

Step 1

In a 9 1/2-to 10-quart heavy kettle simmer stock ingredients, uncovered, 30 minutes. Transfer crab legs with tongs to a work surface and cool until they can be handles. Simmer stock 15 minutes more and pour through a large fine sieve into a large bowl. Return stock to kettle and keep warm, partially covered.

　　

Step 2

Cut open crab shells with shears and remove meat, discarding shells and cartilage. Cut king crab meat into bite-size pieces and transfer to a small bowl.

　　

Step 3

In a heavy skillet (preferably cast-iron) cook oil and flour over moderately low heat, stirring constantly with a flat-edged metal or wooden spatula, until roux od the dark reddish-brown color of chestnut shells, about 45 minutes. (Alternatively, make Microwave Brown Roux , and transfer to skillet.) Roux may be made 1 week ahead, cooled completely, and chilled, covered, in a glass or stainless-steel bowl. Reheat roux in skillet over moderately low heat, stirring, before proceeding. Add onions, bell pepper, and celery and cook, stirring occasionally, until vegetables are softened.

　　

Step 4

Add roux mixture by large spoonfuls to hot stock, stirring well after each addition, and bring to a boil, stirring. Simmer gumbo, stirring occasionally, 15 minutes. Add shrimp and simmer, stirring, 2 minutes. Stir in king crab meat, lump crab meat, and oysters with their reserved liquor and simmer, stirring occasionally, until edges of oysters begin to curl, about 2 minutes. Stir in scallions, cayenne, and salt to taste. Gumbo may be made 1 day ahead, cooled completely, uncovered, and chilled, covered.

　　

Step 5

Serve gumbo ladled over rice in large soup plates.