Heat a large saucepan and add 1 tablespoon of the oil. When hot, add the shrimp shells and cook, stirring, until fragrant and pink, 3 to 4 minutes. Add 10 cups of water and bay leaf and bring to a boil. Reduce the heat to a simmer, and cook, skimming any foam that rises to the surface, for 30 minutes. Strain through a fine mesh strainer and discard solids. Set shrimp stock aside.
In a heavy bottomed Dutch oven or soup pot, heat the 1 cup vegetable oil and, when hot, whisk in the flour. Cook, stirring constantly, until a roux is formed the color of dark peanut butter, about 7 minutes. Add the onion and cook until soft, 4 to 6 minutes. Add the garlic and 2 tablespoons of parsley and cook for 1 minute. Add the potatoes, 8 cups of the reserved shrimp stock, the salt, cayenne, and black pepper and bring to just to a boil. Reduce heat to a simmer and cook until the potatoes are very tender and the sauce is thickened, 30 to 40 minutes. Add the andouille sausage and cook partially. Drain some of the fat and add shrimp, remaining 2 tablespoons parsley, green onions and red chile pepper and stir to combine. Remove from the heat and let sit for 5 minutes. Serve immediately over hot white rice in shallow bowls.
Yield: 2/3 cup
Recipe from "New New Orleans Cooking", by Emeril Lagasse and Jessie Tirsch, published by William Morrow, 1993.