Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 7 minutes; drain.

Combine cornstarch, salt, parsley, garlic powder, and onion powder in a small bowl.

Pour cornstarch mixture, milk, beef stock, and egg noodles into the skillet; bring to a boil. Cover, reduce heat, and simmer, stirring occasionally, until noodles are tender, about 5 minutes. Stir in sour cream and Parmesan cheese until just combined.