Step 1: In a mixing bowl, toss the chicken pieces with olive oil, Cajun seasoning, and smoked paprika until evenly coated.

Step 2: Bring a large pot of salted water to a boil. Cook the spaghetti according to package instructions until al dente, about 9 to 11 minutes. Drain and set aside.

Step 3: While the spaghetti cooks, heat a large skillet over medium-high heat. Add the seasoned chicken and cook for 6 to 8 minutes, stirring occasionally, until browned and fully cooked through. Remove the chicken from the skillet and set aside.

Step 4: In the same skillet, melt the butter over medium heat. Add the minced garlic and cook for about 1 minute until fragrant.

Step 5: Whisk in the flour and stir constantly for 1 minute to form a roux. Gradually pour in the milk and chicken broth, whisking continuously to create a smooth sauce. Bring to a gentle simmer and cook for 3 to 4 minutes until the sauce slightly thickens.

Step 6: Lower the heat and stir in the cream cheese until fully melted and the sauce is smooth. Add 1½ cups mozzarella cheese and all the Parmesan cheese, stirring until melted and creamy. Season with salt, pepper, and optional red pepper flakes. Add the cooked spaghetti and chicken back into the skillet. Toss well to coat the noodles evenly with the sauce.

Step 7: Transfer the mixture to a large oven-safe dish or skillet. Sprinkle the remaining ½ cup of mozzarella cheese on top.

Step 8: Broil for 2 to 3 minutes until the cheese is melted and bubbly.

Step 9: Serve immediately and enjoy the rich, flavorful Cajun chicken spaghetti!