Cook egg noodles al dente in boiling salted water according to package instructions. (For optimal timing, I recommend actually adding the egg noodles to the boiling water at the same time that the beef broth is added to the stroganoff.) Meanwhile, as your pasta water is coming to a boil, melt the butter in a large saute pan** over medium-high heat. Add the steak in a single layer, seasoned with a few generous pinches of salt and pepper, and let it cook undisturbed for about 3 minutes to get a good sear. Flip the steak, and cook on the other side until browned, about another 3 minutes. Then remove steak from pan with a slotted spoon, and transfer to a separate plate. Set aside. (**If your pan is not big enough to fit all of the steak in a single layer, then add just 1 Tbsp. of butter to the pan and cook half of the steak. Then repeat with a second batch.**) Return pan to heat and add the remaining 2 Tbsp. butter. Once it has melted, add the onions and saute for about 3 minutes. Add garlic and mushrooms, and stir to combine. Continue sauteing for an additional 5-7 minutes, or until the mushrooms are cooked and the onions are soft. Add the white wine, and deglaze the pan by using your cooking spoon to scrape the brown bits off the bottom of the pan. Let the mixture cook down for an additional 3 minutes. Meanwhile, in a separate bowl, whisk together the beef broth, worcestershire sauce and flour until smooth. Pour the beef broth mixture into the pan, and stir to combine. Let the mixture simmer for 5 minutes, stirring occasionally. Then stir in the Greek yogurt (or sour cream) until combined, and then stir the cooked steak back in. Season with additional salt and pepper if needed. Serve over the egg noodles, garnished with parsley if desired.