Cook spaghetti in salted boiling water until al dente. Drain and set aside.
Season chicken with Cajun seasoning, smoked paprika, salt, and pepper. Press grated Parmesan onto each piece.
Heat olive oil and 2 tbsp butter in a skillet over medium-high heat. Sear chicken 4–6 minutes until golden.
Add 1 tbsp butter and half the garlic during the last minute. Stir until fragrant, then remove chicken.
Add remaining butter to the skillet. Add the remaining garlic and sauté 30 seconds.
Pour in heavy cream and chicken broth. Bring to a gentle simmer.
Add cream cheese and whisk until fully melted. Stir in mozzarella, cheddar, and Parmesan. Add Italian seasoning, basil, and red pepper flakes.
Let the sauce thicken 2–3 minutes. Add spaghetti directly into the sauce and toss until creamy and coated.
Plate the pasta and top with Parmesan-crusted chicken. Garnish with fresh parsley.
