Boil salted water and cook penne until al dente, reserving some pasta water before draining so you can adjust sauce consistency later.
Sear chicken pieces in olive oil over medium-high heat until golden and fully cooked, ensuring they develop flavor and stay juicy.
Cook onion in butter until soft, then add garlic briefly to build a flavorful base without burning it.
Pour in broth and cream, then simmer gently while stirring to create a smooth and rich sauce.
Add Parmesan cheese and stir until melted, then return chicken and combine everything evenly.
Toss cooked pasta into the sauce, adjusting consistency with reserved pasta water, and cook briefly to bring it all together.