- Melt the butter in a large skillet over medium heat. Add the green bell pepper, onion, celery, and garlic and cook until the vegetables become tender, stirring occasionally, about 5 minutes. 
- Stir in the Cajun seasoning and cook for 1 minute for the spices to bloom and become fragrant. Sprinkle with the flour and cook for 1-2 minutes so the flour loses its raw flavor. 
- Stir in the chicken broth (or water or shrimp stock), then the diced tomatoes, thyme, bay leaf, kosher salt, black pepper, cayenne pepper, and hot sauce. Bring to a simmer then reduce to low and cook for 20-25 minutes or until thickened, stirring occasionally. Add more broth or water as needed. 
- Add the shrimp and cook just until opaque and cooked through, about 5 minutes. Add more broth or water if the broth is too thick. Taste for seasoning then sprinkle with green onion and chopped parsley, and serve over white or brown rice.