Combine the onion, bell pepper and celery, then remove 1/2 cup of the mixture and set aside for later. TO MAKE THE BROWN ROUX: Over high heat in a small heavy saucepot, heat 6 tablespoons of the oil. When hot, add the flour and, with a wooden spoon, over medium heat, stir constantly until the roux turns brown and smells nutty, about 8 to 10 minutes. Remove the pot from the heat and immediately add the reserved 1/2 cup of the vegetable mixture and continue to stir until the roux has cooled down. Transfer the roux, which is very hot, to a mixing bowl. In a heavy 4-quart saucepan, over medium heat, heat the remaining 2 tablespoons of oil. Add the remaining vegetable mixture and cook, stirring, for a couple of minutes. Add the andouille sausage, optional "Cajun" or "Creole" seasoning, cover and cook over low heat for about 5 minutes, or until the vegetables are tender, but not brown. Over medium heat, add the chicken stock, Worcestershire sauce, tomatoes, beans and the reserved roux and bring the liquid to a simmer. Cook, uncovered, for 5 minutes then add the chicken and cook for 5 minutes longer or until the chicken is completely cooked through. Remove the pot from the heat and add the hot sauce if you like your gumbo hot and/or add the sour cream if you like it rich. Serve over rice. Per serving: 1801 Calories (kcal); 158g Total Fat; (77% calories from fat); 18g Protein; 84g Carbohydrate; 102mg Cholesterol; 528mg Sodium Food Exchanges: 3 Grain(Starch); 0 Lean Meat; 4 Vegetable; 0 Fruit; 31 1/2 Fat; 1/2 Other Carbohydrates Converted by MM_Buster v2.0n.