Bring a large pot of salted water to a boil. Add the 8 oz of egg noodles and cook according to package instructions until al dente, usually about 7-8 minutes. Drain the noodles, drizzle with a little olive oil to keep them from sticking, and set aside.
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the thinly sliced beef sirloin and season lightly with salt and pepper. Cook until browned but not fully cooked through, about 2-3 minutes per side. Remove the beef from the pan and set aside.
In the same skillet, add the remaining 1 tablespoon of olive oil. Add the sliced mushrooms and diced onion. Cook, stirring occasionally, until the mushrooms release their moisture and the onions become translucent, about 5-7 minutes. Add the minced garlic and cook for another minute until fragrant.
Sprinkle the 2 tablespoons of flour over the mushroom and onion mixture. Stir well to coat everything evenly. Slowly pour in the 1 cup beef broth while stirring constantly to avoid lumps. Bring the mixture to a gentle simmer. Add the Worcestershire sauce and let the sauce thicken for 3-4 minutes.
Lower the heat to medium-low. Stir in the 1 cup sour cream until the sauce is smooth and creamy. Return the cooked beef to the skillet and stir to combine. Let everything warm through for another 2-3 minutes. Taste and adjust seasoning with salt and pepper.
Add the cooked egg noodles to the skillet, tossing gently to coat the noodles evenly with the creamy mushroom beef stroganoff sauce. Garnish with freshly chopped parsley for a pop of color and freshness.