Add uncooked pasta. Cover with water. Bring to boil and cook 10-12 minutes until al dente, stirring occasionally.
Lower heat. Stir in heavy cream, Parmesan, and red pepper flakes. Simmer for 2-3 minutes.
Return cooked steak cubes to pot. Stir and cook for 2 more minutes to heat through.
Turn off heat. Sprinkle chopped parsley and stir. Serve hot.
Notes
Store leftovers in the fridge for up to 3 days. For freezing, cool and portion into containers. Reheat gently with a splash of cream or water to restore the creamy texture.