Bring a large pot of salted water to a boil. Add pasta and cook according to package instructions for 8-10 minutes until al dente. Reserve a cup of pasta water, drain, and set aside.

Melt 2 tablespoons of butter in a large skillet over medium heat. Add diced chicken, season with salt and pepper, and sauté for 6-8 minutes until golden brown. Remove and keep warm.

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

Pour in heavy cream and chicken broth, stir in Italian seasoning and red pepper flakes. Simmer for about 5 minutes to thicken.

Return chicken and pasta to the skillet, tossing to combine. Cook for an additional 2 minutes.

Plate pasta, top with grated Parmesan cheese and serve warm.