In a deep dish skillet, add ground beef (could add 1/2 chopped onion too). Cook over medium high heat until browned. Drain grease and return meat to pan. Season with Worcestershire sauce and mix well.
Add cornstarch, salt and pepper and mix. Stir in milk and beef broth. Add uncooked pasta. Cook over medium heat until boiling. Cover and reduce heat to low and continue to boil, stirring occasionally for about 12 minutes or until pasta is as tender as you'd like it to be.
Stir in sour cream and top with chopped fresh parsley, if desired, before serving. Allow to sit for at least 5 minutes to thicken for best results. Will continue to thicken as it sits and cools.
Notes
* You can fold in 1/2 can of cream of mushroom soup at the same time as the sour cream if you want it creamier with a thicker sauce