In a large heavy sauce pan, over medium-high, heat 2 tablespoons of oil. Season the duck pieces with Essence. Sear the duck pieces for 2 minutes on each side. Remove from the pan and set aside. Add the remaining oil to the pan. Whisk in the flour. Cook the mixture for about 10-12 minutes for a dark roux, or until the mixture is the color of chocolate and has a nutty aroma. The roux has to be stirred continuously to prevent it from burning. Stir in the vegetables. Season with salt and cayenne. Cook the vegetables for about 8-10 minutes, or until the vegetables start to wilt. Stir in the bay leaves and smoked sausage. Slowly stir in the water and bring to a boil. Reduce to a simmer and cook for 1 1/2 to 2 hours, skimming off the fat occasionally. Stir in the green onions. Ladle the gumbo into a bowl and garnish with rice.
Combine all ingredients thoroughly and store in an airtight jar or container.
Recipe from "New New Orleans Cooking", by Emeril Lagasse and Jessie Tirsch. Published by William and Morrow, 1993.