Bring a large pot of salted water to a boil over high heat. Add your pasta of choice and cook according to package instructions until al dente, usually about 8-10 minutes. Reserve 1 cup of pasta water and drain the pasta.

In a large skillet over medium heat, melt butter until bubbly. Add diced chicken, seasoning with salt and pepper. Cook for about 6-8 minutes until golden brown and cooked through, then remove from skillet.

In the same skillet, add remaining butter, then add minced garlic and diced onion. Sauté for 3-4 minutes until the onion is translucent and garlic is fragrant.

Pour in heavy cream and chicken broth, stirring gently. Add Italian seasoning and red pepper flakes. Simmer for about 5 minutes until the sauce thickens slightly.

Return the sautéed chicken and drained pasta to the skillet, tossing until coated. Cook for an additional 2 minutes over medium heat.

Remove from heat, sprinkle Parmesan cheese over the top, and garnish with fresh parsley before serving warm.