Preparing the Shrimp: Set aside 4 to 6 whole unpeeled shrimp for final decoration. Shell the rest of the shrimp as follows: hold the body in one hand, grasp the head in the other and snap it back and off. Pinch the feet at the tail end and pull them off. Working from the underside of the shrimp, peel the shell from the body, removing the tail with it. To remove the intestinal vein (the black or greenish vein that may or may not be visible along the curve of the back), lay the shrimp on its side on the counter and with a sharp knife make a long slit along the back. With the tip of the knife, scrape out and discard the vein. Rinse the shrimp one at a time under cold tap water.

Preparing the Sauce Base: Mix together the ingredients for the mirepoix. Heat the roux in the saucepan, stirring continuously. Still stirring, and when very hot, slide in the mirepoix vegetables. Cook, stirring rather slowly, for 2 to 3 minutes over high heat, until the onions are translucent. Remove from heat, and vigorously beat in the beer, whisking until smooth. Return the pan to the burner and over moderately high heat add the bay leaves and whisk while gradually pouring in the stock. Continuing to whisk, add 1 tablespoon of the Creole seasoning, the hot pepper sauce, and the Worcestershire sauce; salt to taste. Simmer slowly for 20 minutes, and again correct seasoning.

Ahead-of-Time Note: The sauce may be made up to 3 days in advance; when cool, cover and refrigerate. Heat to bubbling before proceeding.

Adding the Shellfish: Sprinkle the shellfish with the remaining Creole seasoning; stir the shellfish, including those reserved for decoration, into the bubbling sauce, and simmer for 2 to 3 minutes, until the shrimp turn pink. Taste carefully for seasoning.

Serving Shrimp Étouffée: Spoon a portion of hot rice into the center of each warm dinner plate, and surround with a serving of shrimp and sauce. Place one of the reserved unpeeled shrimp decoratively on top of the rice and top it with a big spoonful of sauce. Scatter the green onions over both shrimp and rice, and sprinkle Creole seasoning over all, including a dusting at the edges of the plate.