In a large heavy pot, whisk together the flour and oil over medium heat. Stir continuously for 20 to 25 minutes until it darkens to a chocolate brown colour. This roux is the heart of the gumbo. Keep stirring with patience and care to avoid burning.

Add the chopped onion, bell pepper and celery to the roux. Stir and cook for 5 minutes until the vegetables soften. Add the garlic and cook for 1 minute more. This mixture is known as the holy trinity in Cajun cuisine.

Stir in the bay leaves, thyme, paprika, cayenne, salt and black pepper. Mix well and cook for 2 minutes to allow the flavours to develop and blend into the base.

In a separate frying pan, brown the sausage slices on both sides until caramelised. Remove and set aside. In the same pan, brown the chicken pieces until golden. Browning adds essential flavour, so do not skip this step.

Add the browned sausage and chicken to the gumbo pot. Pour in the chicken stock and stir to combine. Bring the mixture to a gentle boil, then reduce to a low simmer and cook uncovered for 45 minutes. Stir occasionally to prevent sticking.

Once the gumbo has simmered and thickened slightly, stir in the prawns. Cook for 5 to 7 minutes until they are pink and just firm. Do not overcook or they will become tough.

If using filé powder, stir it in now and cook for 2 to 3 minutes more. Filé adds a slight earthiness and thickens the gumbo gently. Do not boil after adding it.

Taste your gumbo and adjust the seasoning if needed. You may want a pinch more salt, a sprinkle of cayenne or another dash of thyme. Let the gumbo sit for 10 minutes to settle before serving.

Ladle the gumbo over hot cooked rice in shallow bowls. Sprinkle each portion with chopped parsley and sliced spring onions for a fresh finish and contrast.

Serve your gumbo hot, with a piece of crusty bread or cornbread on the side. Place hot sauce on the table for those who like an extra punch. Gumbo tastes even better the next day, so feel free to make it ahead.