Make roux from butter and flour. Add celery, onion, parsley, green pepper, and garlic. Simmer for 15-20 minutes over low heat. At stock/water and bay leaves, simmer for 20 mins. Stir in tasso and sausage, simmer 30 min. Bring to a boil while stirring to avoid sticking. Add crawfish, thyme, salt and pepper. Simmer for 15 mins. Drop heat, stir in filé powder, and serve over rice.