How to Make It
Season the chicken with 1 teaspoon salt and 1/2 teaspoon pepper. In a large heavy pot, heat the oil over medium high heat until hot. Sear the chicken, turning once, until browned, about 6 minutes. Transfer the chicken to a plate. Add the sausage to the pan and brown, turning once, 4 to 6 minutes. Transfer the sausage to the plate with the chicken. Stir the bacon fat into the pan and whisk in the flour. Reduce the heat to medium low and cook the flour, stirring frequently until it is several shades darker (about the color of natural peanut butter) an fragrant, about 20 minutes.
Stir in the onion, bell pepper and celery and increase the heat to medium and cook until the vegetables are softened, 8 to 10 minutes. Whisk in the stock and water and bring to a simmer. Add the chicken, sausage along with any accumulated juices and rice, and simmer until the chicken is cooked through, about 30 minutes. Stir in the spinach and cook until tender, about 3 minutes. Season the gumbo with salt and pepper to taste.