Gather ingredients: chicken (or seafood/gumbo mix), andouille sausage, onion, bell pepper, celery, garlic, okra (optional), bay leaves, thyme (or seasoning), salt, black pepper, cayenne (to taste), gumbo file (optional), vegetable oil, all-purpose flour, chicken stock (or seafood stock)
Cut chicken into bite-size pieces and season with salt, black pepper, and cayenne
Slice andouille sausage and mince onion, bell pepper, and celery
Make the roux: heat oil in a heavy pot over medium heat
Add flour to the hot oil gradually while stirring constantly
Cook roux, stirring continuously, until deep brown (dark chocolate color), about 15–30 minutes
Add the “holy trinity” (onion, bell pepper, celery) to the roux and cook until softened, stirring often
Add garlic and cook 30–60 seconds
Stir in stock gradually (start with a few cups to loosen roux), then add remaining stock to reach desired thickness
Add bay leaves, thyme, and any additional seasonings
Brown the chicken in a separate pan (or in the same pot briefly) and add to the gumbo base
Add sliced andouille sausage to the pot
Simmer 45–75 minutes, stirring occasionally, until chicken is tender and flavors meld
Add okra (if using) during the last 20–30 minutes of simmering
Adjust seasoning (salt, black pepper, cayenne) to taste
If using seafood gumbo, add seafood (shrimp/crab/oysters) during the last 5–10 minutes only
Thicken at the end: remove from heat and stir in gumbo file (if using), 1–2 teaspoons at a time, until desired thickness
Remove bay leaves and serve hot
Serve with rice (white or long-grain), and optionally garnish with sliced green onions or parsley