Bring a large pot of salted water to a boil and cook the egg noodles according to package directions. Drain and set aside, reserving 1/2 cup pasta water.
Pat the beef dry and season with salt and pepper. Melt 1 tablespoon butter in a large skillet over medium-high heat. Sear the beef in batches, about 1 1/2 minutes per side, until deeply browned. Transfer to a plate.
Add 1 tablespoon butter to the skillet. Add the onion and cook 2-3 minutes until softened. Add the mushrooms and cook 5-6 minutes, until they release their liquid and it evaporates. Add the garlic and cook 30 seconds.
Sprinkle the flour over the vegetables and stir for 1 minute. Slowly whisk in the beef broth, then add the Worcestershire sauce and Dijon mustard. Simmer 3-4 minutes until thickened, scraping up the browned bits from the pan.
Reduce heat to low. Whisk a few tablespoons of the hot sauce into the sour cream to temper it, then stir the tempered sour cream into the skillet.
Return the seared beef to the skillet and warm through for 1-2 minutes without boiling. Thin with reserved pasta water if needed.
Serve over the egg noodles, topped with parsley.