Cut chicken into bite-sized pieces and season with Cajun seasoning and smoked paprika. Let marinate for about 10 minutes.

Cook spaghetti in boiling salted water according to package instructions until al dente, about 8-10 minutes. Drain and set aside.

Heat a skillet over medium-high heat with a splash of oil. Add chicken in a single layer, cooking for 6-8 minutes until browned and cooked through. Set chicken aside.

In the same skillet, reduce heat to medium. Melt butter, then add minced garlic and sauté for 1 minute. Whisk in flour and cook for another minute to form a roux.

Gradually pour in milk and chicken broth while whisking. Simmer for 3-4 minutes until thickened.

Reduce heat to low, add cream cheese, stirring until melted. Mix in mozzarella and Parmesan until melted and smooth.

Add spaghetti and cooked chicken to skillet. Toss gently to coat thoroughly in the sauce.

Preheat broiler. Transfer to an oven-safe dish, sprinkle extra mozzarella on top, and broil for 2-3 minutes until bubbly and golden.

Serve immediately, garnished with parsley or red pepper flakes if desired.