Cook pasta in a large pot of salted boiling water for 8 to 10 minutes until al dente. Reserve 1 cup of pasta water, drain and set aside.

In a skillet, melt 2 tablespoons of butter over medium heat. Season chicken breast with salt and pepper, then cook for 6 to 8 minutes until golden brown and cooked through. Remove and let rest.

In the same skillet, melt remaining butter. Add minced garlic and diced onion, sauté for 3 to 4 minutes until translucent.

Stir in heavy cream and chicken broth with Italian seasoning and red pepper flakes. Simmer for about 5 minutes until slightly thickened.

Cut chicken into bite-sized pieces and return it to the skillet. Add drained pasta and gently toss to coat in the sauce. Heat through for another 2 minutes.

Remove from heat and serve topped with grated Parmesan cheese and parsley.