Bring pot of water to a boil. Cook Fettuccine to package directions. Drain, rinse and set aside. Spray a 2 quart casserole dish with non- stick spray. Set aside
In a large skillet over medium heat melt butter. Add chopped onion,celery, and bell pepper and cook until soft.Stir in flour and cook for 3 minutes.Add parsley, seasoning, and crawfish tails and cook on simmer for 15 minutes.Add in half and half and cubed velvetta, and continue cooking over low until cheese is melted. add the cooked fettuccine and stir well. Transfer to baking dish and sprinkle with parmensan cheese.