Bring a large pot of salted water to a rolling boil and add the spaghetti. Cook for 8-10 minutes, or until al dente, stirring occasionally to prevent sticking. Once done, reserve 1/2 cup of the pasta water, then drain the spaghetti in a colander and set aside.

In a large skillet over medium-high heat, add the ground beef and break it into pieces using a spatula. Season with Cajun seasoning, salt, and pepper, cooking until the beef is browned and no longer pink, approximately 5-7 minutes. Once cooked, drain excess fat and move the beef to one side of the skillet.

Lower the heat to medium, and add two tablespoons of unsalted butter to the same skillet. Once melted, add the minced garlic to the butter and sauté for about 30 seconds, just until fragrant.

Pour in 1 cup of heavy cream and 1/2 cup of chicken broth, allowing the mixture to shimmer gently over medium heat. Whisk in the softened cream cheese until fully integrated, then slowly stir in the shredded cheddar, mozzarella, and Parmesan cheese. Continue mixing until all cheese is melted and the sauce is smooth and creamy.

Add the reserved spaghetti to the skillet, gently tossing everything together to coat the noodles in the cheese sauce. Incorporate the browned beef and fold to combine well.

Taste the creamy Cajun beef spaghetti and adjust the seasoning with more salt, pepper, or Cajun seasoning if desired. Serve immediately, garnished with fresh parsley, extra Parmesan cheese, and a sprinkle of Cajun seasoning.