In your large pot, combine the flour and oil over medium-low heat. Stir constantly with a wooden spoon for about 30–45 minutes. You’re aiming for a dark brown roux, something like melted chocolate. This is the backbone of your gumbo—be patient and don’t rush it.
Once the roux reaches the right color, add in your chopped celery, bell pepper, and onion. This “holy trinity” of Cajun cooking will start sizzling right away. Stir everything together and cook for about 5–7 minutes, until the vegetables soften and the mixture becomes fragrant.
While the veggies are cooking, heat a small skillet and sear your sausage slices until golden brown on both sides. This extra step really brings out the smoky flavor and helps them hold their texture in the gumbo.
Add your garlic and Cajun seasoning into the pot, stirring for a minute. Then pour in the chicken broth and toss in the cooked sausage. Bring everything to a gentle boil. You’ll probably see some foam rise—skim that off for a cleaner broth.
Now stir in your shredded rotisserie chicken. Let it simmer for about 10 minutes. After that, add the shrimp and let it cook just until it turns pink and opaque. Don’t overcook the shrimp; they only need a few minutes.
Scoop some fluffy white rice into serving bowls and ladle the gumbo right on top. Garnish with green onions and a sprinkle of parsley. If you like a little kick, add hot sauce at the table. It’s a flavor party!