This recipe uses a whole chicken to build a flavorful broth and meat base. The key is the dark, rich roux and the "holy trinity" of vegetables.
If starting with a raw whole chicken, place it in a large pot with 2-3 quarts of water, some celery, and salt. Bring to a boil, then reduce to a simmer and cook until the chicken is fall-off-the-bone tender (approximately 1.5 hours) or cook for 1 hour on high pressure in an Instant Pot. Remove the chicken, shred the meat, and set it aside. Strain the cooking liquid—this is your rich chicken stock. Set the stock aside.
In a large, heavy-bottomed pot or Dutch oven (the one you'll make the gumbo in), heat the 1 cup of vegetable oil over medium heat. Gradually whisk in the 1.5 cups of flour. Continue to cook over medium-low to medium heat, whisking constantly, for 20-30 minutes. You are aiming for a rich, dark chocolate brown color.⚠️ Warning: Do not walk away! The roux can burn quickly once it starts to darken. If it burns (you'll see black flecks), you must start over.
Once the roux reaches the desired dark color, reduce the heat to low. Add the diced onion, celery, and bell pepper (the "holy trinity") directly into the roux. Stir frequently and cook until the vegetables have softened and become translucent, about 5-7 minutes. They will absorb the roux and release a wonderful aroma.
Add the sliced andouille/smoked sausage to the pot and stir to coat. Begin to add the 12 cups of chicken stock/broth. Pour the stock in slowly while continuously whisking the roux mixture to prevent clumping. Use a room-temperature or warm stock if possible. Once all the stock is incorporated and the mixture is smooth, increase the heat to bring the liquid to a boil, then immediately reduce the heat to a low, gentle simmer. Add your seasonings: generous pinches of Cajun seasoning, garlic powder, onion powder, black pepper, dried thyme, and a dash of cayenne pepper. Taste the broth and adjust seasonings as needed, keeping in mind the sausage is salty. Cover the pot and let the gumbo simmer for a minimum of 1 hour (up to 2 hours) to allow the flavors to deepen and marry. Stir occasionally.
After the long simmer, stir in the reserved, shredded cooked chicken meat into the gumbo. Continue to simmer, uncovered, for an additional 10-15 minutes, allowing the chicken to warm through and absorb the gumbo flavor. Taste and make any final adjustments to salt or pepper. Serve the gumbo hot over a scoop of cooked white rice. Garnish with chopped green onions or parsley, and enjoy with a side of potato salad!