Cook the Pasta: Bring a large pot of salted water to a boil. Cook rotini according to package instructions until al dente. Reserve ½ cup pasta water, then drain and set aside.

Cook the Chicken: In a large skillet, heat olive oil over medium-high heat. Season chicken pieces with salt, black pepper, smoked paprika, and Italian seasoning. Add chicken to the skillet and cook for 4-5 minutes per side until golden brown and cooked through. Remove from the skillet and set aside.

Make the Parmesan Garlic Butter Sauce: In the same skillet, melt butter over medium heat. Add minced garlic and sauté for 30 seconds until fragrant. Pour in chicken broth and heavy cream, stirring well. Bring to a gentle simmer. Gradually add Parmesan cheese and mozzarella (if using), stirring until smooth and creamy. If the sauce is too thick, add reserved pasta water a little at a time until desired consistency is reached. Stir in red pepper flakes (if using) for a little heat.

Combine & Serve: Return the cooked chicken to the skillet, followed by the drained rotini. Toss everything together to coat in the creamy garlic Parmesan sauce. Remove from heat and garnish with fresh parsley. Serve warm with extra Parmesan on top.