In a large pot, whisk the flour and oil together until well blended. Then turn up over medium-high heat and bring to a boil. Reduce to medium and continue to whisk and cook for an extra 5 minutes, until the mixture begins to turn reddish-brown in color.
Stir in the onion, red pepper, apple, celery, and garlic. Cook this mixture for about 5 minutes, stirring occasionally.
Mix in the tomato sauce, 1 cup water, Worcestershire sauce, Cajun seasoning and sweet chili sauce and simmer for 15 minutes.
Meanwhile, make sure to devein and remove the tails and shell of the prawns. Add the shrimp and flat-leafed parsley and simmer about 4-5 more minutes, or until the prawns have turned a nice pink and opaque color.
Serve the prawns and sauce over brown rice. Garnish with a wedge of lemon.
Recipe by Just a Smidgen at https://justasmidgen.com/2012/11/22/sweet-and-spicy-prawn-etouffee/