Creole-Style Shrimp And Sausage Gumbo

1. Bring reserved shrimp shells and 4-1⁄2 cups water to boil in stockpot or large saucepan over medium-high heat. Reduce heat to medium-low and simmer for 20 minutes. Strain stock and add ice water and clam juice (you should have about 8 cups of tepid stock, 100 to 110 degrees); discard shells. Set stock aside.
2. Heat oil in Dutch oven or large saucepan over medium-high heat until it registers 200 degrees on instant-read thermometer, 1-1⁄2 to 2 minutes. Reduce heat to medium and gradually stir in flour with wooden spatula or spoon, making sure to work out any lumps that may form. Continue stirring constantly, reaching into corners of pan, until mixture has toasty aroma and is deep reddish brown, about 20 minutes. (Roux will thin as it cooks; if it begins to smoke, remove pan from heat and stir roux constantly to cool slightly.)
3. Add onions, bell pepper, celery, garlic, thyme, 1 teaspoon salt, and 1⁄4 teaspoon cayenne to roux and cook, stirring frequently, until vegetables soften, 8 to 10 minutes. Add 4 cups reserved stock in slow, steady stream while stirring vigorously. Stir in remaining 4 cups stock. Increase heat to high and bring to boil. Reduce heat to medium-low, skim foam from the surface with wide spoon, add bay leaves, and simmer, uncovered, about 30 minutes, skimming foam as it rises to surface. (Mixture can be covered and set aside for several hours or refrigerated up to 2 days. Reheat when ready to proceed.)
4. Stir in sausage and continue simmering to blend flavors, about 30 minutes. Stir in shrimp and simmer until cooked through, about 5 minutes. Off heat, stir in parsley and scallions and season with salt, pepper, and cayenne to taste. Discard bay leaves and serve immediately.

SHRIMP AND SAUSAGE GUMBO WITH OKRA
Fresh okra may be used in place of frozen, though it tends to be more slippery, a quality that diminishes with increased cooking. Substitute an equal amount of fresh okra for frozen; trim the caps, slice the pods 1⁄4 inch thick, and increase the sautéing time with the onions, bell pepper, and celery to 10 to 15 minutes.
Add 10 ounces thawed frozen cut okra to roux along with onions, bell pepper, and celery.

SHRIMP AND SAUSAGE GUMBO WITH FILÉ
Add 1-1⁄2 teaspoons filé powder along with parsley and scallions in step 4 after gumbo has been removed from heat. Let rest until slightly thickened, about 5 minutes. Adjust seasonings and serve.