Heat olive oil in a large pot over medium-high heat.
Add sliced beef sirloin, seasoning lightly with salt and pepper, and cook until browned.
Remove the beef from the pot and set aside, leaving any drippings behind.
Add the chopped onion and sliced mushrooms to the pot, cooking until softened, about 5 minutes.
Stir in minced garlic and cook for an additional minute until fragrant.
Sprinkle the flour over the vegetables, stirring to combine, and cook for another minute.
Pour in beef broth and Worcestershire sauce, scraping any browned bits from the bottom of the pot.
Bring the mixture to a simmer, then reduce heat to low and let it cook for 10 minutes.
Return the browned beef to the pot, stirring to coat in the sauce.
Stir in sour cream until fully incorporated and warm.
Cook the egg noodles according to package instructions; drain and set aside.
Serve the stroganoff over the noodles, garnished with fresh parsley if desired.