Heat olive oil in a skillet over medium-high heat and season red snapper fillets with salt and black pepper.
Sear the fillets for 4 to 5 minutes on each side until golden brown, then remove from skillet and set aside.
In the same skillet, sauté onion, bell pepper, and celery until softened, about 3 to 4 minutes.
Add minced garlic and cook for an additional minute.
Stir in flour and gradually whisk in chicken broth until the mixture is smooth; bring to a simmer.
Add heavy cream, parsley, Creole seasoning, Worcestershire sauce, and cayenne pepper if using; simmer for 5 to 7 minutes until thickened.
Return the snapper fillets to the skillet and spoon the sauce over the fish, warming through for 2 to 3 minutes.
Serve the snapper and Creole sauce over cooked rice, garnished with additional fresh parsley.