Bring a large pot of salted water to a rolling boil. Toss in your pasta and cook according to the package instructions until al dente (typically 8-10 minutes). Reserve 1 cup of pasta water, then drain the rest and set it aside.
Melt 2 tablespoons of butter in a large skillet over medium heat. Add the diced chicken pieces, seasoning them with salt and pepper. Cook for about 6-8 minutes until the chicken is golden brown and fully cooked through, then remove the chicken from the skillet and set aside.
In the same skillet, add the remaining butter. Sauté minced garlic and diced onion until they turn translucent (about 3-4 minutes).
Pour in the heavy cream and chicken broth, stirring to combine. Add the Italian seasoning and red pepper flakes, letting the sauce simmer gently for about 5 minutes until it thickens slightly.
Return the cooked chicken and drained pasta to the skillet. Adjust seasoning with additional salt and pepper if needed. Toss everything together to ensure the chicken and pasta are well-coated in the creamy sauce, letting it cook for another 2 minutes.
Sprinkle grated Parmesan cheese over the top, allowing it to melt into the dish. Garnish with fresh parsley before serving.
