Prawn gumbo

Name: Prawn gumbo
Ingredients: 300 g canned okra, rinsed and drained; 425 g can tomatoes; 60 g butter; 2 cups chopped Cajun vegetables; 2 cloves garlic, chopped; 2 teaspoons tomato paste; 2 teaspoons Cajun spice mix; 2 bay leaves; 1/4 teaspoon ground allspice; 2 teaspoons chilli flakes; 1 tablespoon Worcestershire sauce pepper; 2 cups seafood stock; 1/4 cup red-brown roux; 600 g medium green prawns; 1 teaspoon file powder, optional