In a large skillet, melt the butter over medium heat. Add the onions, bell peppers, celery, and garlic. Cook until tender, about 5 minutes. Add the flour and Cajun seasoning and cook for 2 minutes, stirring frequently. Stir in the milk and cook until slightly thickened, stirring constantly, 5 to 6 minutes. Add the soup and cheese, stirring until the cheese is melted. Add the crawfish, and cook until warmed through. Serve over the fettuccini. Garnish with chives, if desired.
Recipe courtesy of Paula Deen