Cook - When roux is ready, stir in onions, celery, green peppers, and garlic. Mix in tomato paste and pour in broth and water. Increase heat to medium and add bay leaves, basil, thyme, chili powder, cayenne pepper, black pepper, and salt. Simmer for 45 minutes. Add scallion, parsley, and shrimp. Cook until shrimp are done, about 20 minutes.