Combine the flour, salt, garlic powder, and cayenne in a plastic or paper bag. Toss the chicken pieces in the mixture until thoroughly coated. Remove the chicken from the bag and reserve 1/2 cup (125 ml) of the flour mixture. Heat the vegetable oil in a large skillet over high heat and fry the chicken until browned on all sides and cooked through, about 8 to 10 minutes per side.
Remove the chicken and set aside. Add the reserved flour mixture to the skillet and cook, stirring up the brown bits on the bottom of the pan, until the flour is dark brown, about 10 minutes. Add the chopped onions, bell peppers, and celery and cook over low heat until the vegetables are tender, about 5 minutes. Meanwhile, bring the chicken stock to a boil in a large pot.
Add the vegetable mixture gradually, stirring constantly. Add the andouille and garlic and simmer uncovered over low heat for 30 to 45 minutes, stirring occasionally. Remove the chicken meat from the bones and cut into 1/2-inch (1 cm) pieces.
Stir the chicken into the gumbo and adjust the seasoning immediately before serving. To serve, place a small amount of cooked rice in individual serving bowls and ladle the gumbo over it. Serves 6 to 8 as a soup course, 4 to 6 as a main dish.
Reproduced by permission of Worldwide Recipes.