Melt butter in a large pot over low heat, and stir in flour. Cook, stirring constantly to make a light roux, about 5 minutes.
Add onions, and cook until wilted. Pour in milk, creamed corn, whole kernel corn, and cream of potato soup. Season with Creole seasoning, Worcestershire sauce, pepper sauce, and salt. Stir to blend, and cook over medium heat for 20 minutes. Add the crawfish, and cook for 20 more minutes.
