|Remove excess fat from the chicken pieces. Rub a generous amount of salt, garlic powder and red pepper on both sides of each piece, making sure each is evenly covered. Let stand at room temperature for 30 minutes.
Meanwhile, in a paper or plastic bag combine the flour, 1/2 teaspoon salt, 1/2 teaspoon garlic powder and 1/2 teaspoon red pepper. Add the chicken pieces and shake until pieces are well coated. Reserve any excess flour.
In a large heavy skillet (preferably cast iron) heat 1 1/2 inches of oil to 375 F. Fry the chicken pieces until both sides are browned and the meat is cooked, about 5 to 8 minutes per side. Drain on paper towels and set aside. Carefully pour the hot oil into a large glass measuring cup, leaving as many of the browned particles in the skillet as possible. Scrape the skillet bottom with a metal whisk to loosen any stuck particles, then return 1/2 cup of the oil to the skillet.
Heat the oil in the skillet over high heat until it starts to smoke, about 5 minutes. (It may take longer if skillet is not cast iron.) Meanwhile, measure out 3/4 cup flour (use the reserved flour from chicken coating and as much additional flour as needed to make 3/4 cup). In a small bowl combine 1/4 cup each of the onions, celery and bell peppers.
When the oil is hot, remove the skillet from the heat and add the flour. Using a long-handled metal whisk, stir until all the flour is blended into the oil. Return the skillet to a medium-high heat and whisk constantly until the roux is dark red-brown to black, about 3 to 4 minutes (being careful not to let it scorch or splash on your skin). Immediately remove roux from heat and whisk in the vegetable mixture. Continue whisking until the roux stops turning darker, about 2 to 3 minutes. Set aside.
Bring 3 1/2 cups of the stock to a rolling boil in a 2-quart saucepan. Add the roux mixture by spoonfuls to the boiling stock, stirring until dissolved between each addition. Bring the mixture to a rolling boil again and simmer uncovered over low heat for 15 minutes, stirring fairly constantly. (The etouffee sauce should be the consistency of very thick gravy.) Set aside.
Combine the seasoning mix ingredients in a small bowl; mix well and set aside.
Melt 5 tablespoons of the butter in a large skillet. Add the remaining 1/4 cup each of onions, celery and bell peppers. Saute over very low heat until the vegetables are completely wilted, about 10 to 12 minutes, stirring occasionally. Add the reserved etouffee sauce and the seasoning mix. Simmer 15 minutes longer, stirring frequently.
Heat-the serving plates in a 250 F. oven.
Melt the remaining butter in a 4-quart saucepan over medium heat; add the green onions and saute about 2 minutes. Add the chicken and etouffee sauce and bring to a boil over medium heat. Remove pan from heat and let sit 15 minutes. Skim off surface oil. Reheat the sauce just until well heated. You may need to thin the sauce with additional stock (preferred) or water. (The end result should be a thick brown gravy.) Serve immediately.
To serve, place 1/2 cup of rice and 2 pieces of chicken on each heated serving plate. Top rice with 1/3 cup sauce.