Take the fettuccine pasta out of the package and cook it according to the instructions written on the package. Then drain it and place it on a side, unbothered.
Meanwhile, when the pasta is cooking, take a Dutch oven and add the butter stick to it. Then melt the butter on a medium heat. Then add onion, red bell pepper, and celery and cook for 5-7 minutes until they become soft.
Add minced garlic to the Dutch oven contents and cook them for 2 more minutes. Then add the crawfish meat, black pepper, and cajun seasoning. Give a mix and cook for 3 minutes.
On the cooked crawfish mixture, add the flour by sprinkling and mix it in the fish. Cook again for 1 minute. Add half and half and cook until the mixture starts simmering.
Finally add freshly grated parmesan cheese, sour cream, and Velveeta cheese to the crawfish meat. On medium heat cook everything together until all the cheese is melted well enough.
Add the cooked pasta to this mixture. Then add parsley and green onions. Stir so that all the contents are fully mixed into one another. Crawfish Fettuccine is ready. Bon Appetit!