Cook ground beef, onion, and garlic in a 6-quart Dutch oven or large pot until beef is cooked, browned, and no longer pink (about 5 to 6 minutes). Crumble beef with a wooden spoon while cooking. Drain off fat.
Lower to medium heat. Add mushrooms and cook until tender, stirring frequently (about 5 to 6 minutes).
Add flour, 1 tablespoon at a time, stirring well in-between each tablespoon.
Add beef broth, Worcestershire, salt and pepper. Stir to combine. Increase heat to medium high and bring to a gentle boil.
Add egg noodles and stir to combine. Cover and simmer for 10 to 12 minutes, or until noodles are tender and liquid is absorbed. *Remove lid and stir occasionally to prevent noodles from sticking to the bottom of the pot (I stirred 5 times). Adjust heat as necessary to maintain a gentle boil/strong simmer.
Remove from heat and add sour cream. Stir to coat evenly. Sprinkle with fresh chopped parsley when serving, if desired.