Bring a large pot of salted water to a rolling boil over high heat. Add your choice of pasta and cook according to package instructions, usually about 8 to 10 minutes, until al dente. Once cooked, reserve 1 cup of the pasta water in a bowl, then drain the pasta and set it aside.

In a large skillet, melt 2 tablespoons of butter over medium heat. Add diced chicken breast, season with salt and pepper, and sauté for 6 to 8 minutes until the chicken is golden brown and cooked through, stirring occasionally. Once done, remove the chicken from the skillet and set it aside on a plate.

In the same skillet, add the remaining 2 tablespoons of butter. Once melted, toss in minced garlic and chopped onion. Sauté for 3 to 4 minutes until the onion is translucent and fragrant, stirring frequently.

Pour in the heavy cream and chicken broth, stirring well to combine. Sprinkle in Italian seasoning and red pepper flakes. Let the sauce simmer for about 5 minutes, stirring occasionally, until it thickens slightly.

Return the sautéed chicken and the drained pasta to the skillet with the sauce. Gently toss everything together for 2 minutes over low heat.

Sprinkle freshly grated Parmesan cheese over the top and garnish with chopped fresh parsley. Serve warm.