A hearty, deeply spiced heritage soup slow-simmered with tender cuts of meat or seafood and aromatic spices, served steaming hot.
Heat vegetable oil and plain flour in a heavy cast iron Dutch oven over medium-low heat; whisk constantly for 30-40 minutes without stopping until roux turns a rich dark chocolate-brown colour.
Immediately add diced onions, celery, and green bell pepper to the hot roux to stop the cooking; cook for 6 minutes until vegetables soften.
Stir in minced garlic, thyme, cayenne pepper, and bay leaves for 2 minutes.
Slowly ladle in warm chicken stock while whisking constantly to incorporate the roux smoothly; bring to a simmer, then add sliced Andouille sausage and browned chicken pieces.
Simmer uncovered over low heat for 1.5 hours, skimming off surface oil, until chicken is falling off the bone and gumbo is thick and fragrant.
Turn off heat, stir in filé powder; ladle over bowls of hot steamed white rice and scatter with chopped spring onions.