Bring a large pot of salted water to a rolling boil over high heat. Add pasta and cook until al dente, about 8-10 minutes. Reserve ½ cup pasta water, then drain and set aside.

Season cubed chicken with salt, pepper, and Italian seasoning. In a skillet, melt 1 tablespoon butter over medium-high heat. Sear chicken for about 3-4 minutes on each side. Remove chicken and set aside.

In the same skillet, melt remaining butter over medium heat. Sauté minced garlic and red pepper flakes for 30-60 seconds until fragrant. Pour in chicken broth and deglaze the pan. Stir in heavy cream and additional Italian seasoning. Let simmer for 2-3 minutes.

Gradually whisk in Parmesan cheese until melted. If too thick, add reserved pasta water. Adjust seasoning as needed.

Return chicken to skillet with juices, add pasta, and toss until well-coated. Garnish with parsley and serve immediately.