1. Heat olive oil or butter in a large skillet over medium heat. Add chopped onion and sauté until translucent. Stir in minced garlic and cook for 1 minute.

2. Add the ground beef, breaking it up as it cooks. Sauté until browned. Season with Cajun seasoning, salt, and pepper.

3. In a separate pot, cook spaghetti in salted boiling water until al dente. Reserve 1/2 cup of pasta water and drain the rest.

4. Lower the heat under the beef. Stir in cream cheese and let it melt completely. Add heavy cream and mix until smooth.

5. Add mozzarella and Parmesan cheese gradually, stirring continuously to create a creamy sauce.

6. Toss the cooked spaghetti into the skillet. Mix to coat evenly. Use reserved pasta water to adjust sauce thickness if needed.

7. Garnish with chopped parsley and serve hot with extra Parmesan on the side.