Boil salted water in a large pot. Add pasta and cook for 8-10 minutes until al dente. Reserve 1 cup pasta water before draining.

Melt 2 tablespoons of butter in a skillet over medium heat. Cook diced chicken breast seasoned with salt and pepper for about 6-8 minutes until golden brown.

Add another tablespoon of butter to the same skillet, melt, then sauté minced garlic and diced onion for 3-4 minutes until translucent.

Pour in heavy cream and chicken broth. Stir in Italian seasoning and red pepper flakes. Simmer for 5 minutes until slightly thickened, adding reserved pasta water if needed.

Add the cooked chicken and drained pasta to the skillet, mixing to coat all ingredients in the sauce. Cook for an additional 2 minutes.

Serve hot, garnished with grated Parmesan cheese and fresh parsley.