In a large pot, heat the olive oil over medium heat. Add the diced onion and cook until translucent, about 5 minutes.
Add the minced garlic and ground beef to the pot. Cook until the beef is browned, breaking it apart with a spoon, about 5-7 minutes. Drain excess fat if necessary.
Stir in the sliced mushrooms and cook for another 3-4 minutes until they are softened.
Pour in the beef broth, Worcestershire sauce, Dijon mustard, and dried thyme. Bring the mixture to a boil.
Add the egg noodles and reduce the heat to a simmer. Cook until the noodles are tender, about 8-10 minutes.
Remove the pot from heat and stir in the sour cream until well combined. Season with salt and pepper to taste.
Serve hot, garnished with chopped parsley.