Add the ground beef, onion, and minced garlic to a large skillet set over medium-high heat on the stove and season with the salt and pepper. Cook, stirring occasionally, until the meat is almost browned but still slightly pink and the onions have begun to soften, about 5 minutes. Drain any excess grease from the pan.

Add the sliced mushrooms to the ground beef and onions and continue cooking for another 5 minutes or so, until the mushrooms are softened and brown and the meat is fully cooked.

Add the cream cheese to the cooked meat and mushrooms and let it sit for 1-2 minutes to melt somewhat before stirring it into the meat mixture. While the cream cheese melts, combine the beef broth and milk in a separate bowl and whisk in the flour until no lumps remain.

After stirring in the melted cream cheese, pour the beef broth/milk/flour slurry into the pan with the meat and mushrooms and cook for 3-4 minutes, stirring occasionally, until slightly thickened and bubbling.

Remove from the heat and stir in the sour cream. Season with additional salt and pepper, to taste.

Serve over hot buttered egg noodles, sprinkled with freshly chopped parsley, if desired.