Start by heating olive oil in a large skillet over medium heat, then add chopped onion, green bell pepper, and celery, cooking until softened, about 5 minutes.
Stir in minced garlic and cook for another minute before sprinkling flour over the sautéed vegetables; mix well to combine.
Gradually whisk in chicken broth, ensuring there are no lumps from the flour, followed by heavy cream for a velvety texture.
Add Creole seasoning, Worcestershire sauce, cayenne pepper if using, salt, and black pepper; allow it to simmer gently for about 10 minutes while stirring frequently.
In another pan, melt butter over medium heat and place red snapper fillets skin-side down; cook for 3-4 minutes on each side until golden brown and flaky.
Plate your cooked snapper alongside generous spoonfuls of creamy Creole sauce over rice; garnish with fresh parsley before enjoying this delightful meal together!