1. Trim and thinly slice the scallions. Finely chop the onion and the celery. Core, seed, and finely chop the pepper. Rinse and drain the beans.
2. Heat the oil in a large saucepan over high heat until almost smoking. Add the scallions, onion, bell pepper, and celery; reduce the heat to medium and stir the vegetables around with a wooden spoon until tender, about 3 minutes.
3. Add the garlic powder, cayenne, and thyme and stir-fry for a few seconds. Add the broth and mix it in with a whisk. Bring the liquid to a boil, then add the beans and spinach. Cover the pan and simmer over low heat at least 20 minutes to bring the flavors together. You can simmer this up to 1 hour; the longer the stew cooks, the more the flavors meld.
4. Meanwhile cut the poultry into ½-inch cubes and mince the parsley.
5. Right before serving, stir in the chicken and parsley; simmer until the poultry is cooked through, about 5 minutes more. Season to taste with salt and serve hot.
• This becomes a spicy seafood stew by substituting 1 pound crabmeat, sea scallops, or cubed monkfish for the chicken.
• Turn the gumbo into a spicy complementary protein dish by omitting the chicken and adding another can of beans. Serve over rice, millet, quinoa, or pasta.
• Add a cup or two of vegetables, such as chopped carrots or corn kernels, with the beans and spinach, and simmer along with the other ingredients.
• Omit the frozen spinach in step 3 and add ½ pound rinsed and chopped fresh greens, such as Swiss chard, beet greens, or kale, before adding the poultry. Simmer along with the chicken.