Bring a large pot of salted water to a boil. Cook the egg noodles according to package instructions until al dente, about 7-8 minutes. Drain and set aside.
In a medium bowl, combine the flour, salt, and black pepper. Toss the beef strips in the flour mixture until evenly coated.
Heat 1 tablespoon of butter and the olive oil in a large skillet over medium-high heat. Add the beef strips in a single layer and sear until browned on all sides but not fully cooked through, about 2-3 minutes. Remove the beef from the skillet and set aside.
In the same skillet, add the remaining 1 tablespoon of butter. Add the chopped onion and cook until softened, about 3 minutes.
Add the sliced mushrooms and cook until they release their moisture and begin to brown, about 5 minutes.
Stir in the minced garlic and cook for 30 seconds until fragrant.
Pour in the beef broth, Worcestershire sauce, and Dijon mustard. Stir to combine and bring the mixture to a simmer.
Return the beef strips to the skillet and cook for 3-4 minutes, until the beef is cooked through and the sauce has thickened slightly.
Remove the skillet from heat and stir in the sour cream until the sauce is smooth and creamy. Do not boil after adding sour cream to prevent curdling.
Serve the beef stroganoff over the cooked egg noodles and garnish with chopped fresh parsley.