Bring a large pot of salted water to a boil. Add pasta and cook until al dente, about 8-10 minutes. Reserve 1 cup of pasta water before draining.

In a skillet over medium heat, melt 2 tablespoons of butter. Season chicken with salt and pepper, cook for 6-8 minutes until golden brown and cooked through. Remove chicken and set aside.

In the same skillet, add 1 tablespoon of butter, garlic, and onion. Sauté for 3-4 minutes until the onion is translucent.

Pour in heavy cream and chicken broth, stirring to combine. Add Italian seasoning and red pepper flakes. Let it simmer for 5 minutes, adjusting with reserved pasta water as needed.

Return chicken and drained pasta to the skillet, toss everything gently until well coated. Simmer for another 2 minutes.

Plate the pasta and garnish with Parmesan cheese and fresh parsley.