Bring a large pot of salted water to a boil. Cook pasta until al dente according to package instructions. Reserve 1/2 cup of pasta water, then drain and set aside.
Pat chicken dry, season with salt, pepper, and 1/2 tsp Italian seasoning. Heat 1 tbsp butter in a skillet over medium-high heat. Sear chicken for 3–4 minutes per side until golden and fully cooked. Remove and set aside.
In the same skillet, melt remaining butter over medium heat. Add garlic and red pepper flakes; sauté for 30–60 seconds.
Deglaze with chicken broth, scraping up brown bits. Stir in heavy cream and remaining Italian seasoning; simmer 2–3 minutes. Lower heat and whisk in Parmesan until smooth.
Return chicken and juices to the skillet. Add pasta, tossing to coat in the sauce. If needed, add reserved pasta water to loosen the sauce.
Adjust seasoning to taste. Garnish with fresh parsley. Serve immediately.
