Brown flour in butter to a light golden brown over medium heat. Add yellow onions, bell peppers, and celery and cook, stirring constantly until onions are clear. Add green onions and garlic until onions are wilted. Add chicken stock and any juice drained from seafood. Add salt, pepper, paprika, and Tabasco. Cook until gravy doesn’t have a floury taste( approximately 20 minutes). Add crawfish or shrimp tails and cook another 15 minutes. Add Cajun seasoning to taste. Serve over hot rice.