Bring a large pot of salted water to a boil. Cook spaghetti until al dente according to package instructions, usually about 8-10 minutes. Reserve 1/2 cup of the starchy pasta water before draining, then drain the pasta and set aside.

Heat olive oil and butter in a large skillet over medium-high heat. Add ground beef and season with Cajun seasoning, garlic powder, and onion powder. Break beef into smaller pieces and cook until fully browned with slightly crispy edges, about 6-8 minutes. Transfer cooked beef to a plate, leaving about 1 tablespoon of fat in the skillet.

Reduce heat to medium. Add heavy cream and cream cheese to the skillet. Stir constantly, breaking up the cream cheese as it softens, until the mixture is completely smooth, about 2-3 minutes.

Add mozzarella cheese and stir until melted, then add Parmesan cheese. Continue stirring until all cheese is melted and the sauce is thick and creamy. If the sauce is too thick, add reserved pasta water one tablespoon at a time until you reach desired consistency.

Return the cooked spaghetti and browned beef to the skillet. Using tongs, toss everything together until pasta is well coated with sauce. Let simmer gently for 1-2 minutes to allow flavors to meld.

Turn off heat and taste for seasoning, adding salt if needed. Garnish with fresh parsley and serve immediately while hot and creamy.