Boil the pasta in a large pot of boiling salted water until al dente. Strain, set aside.
Melt one tablespoon of butter in a large non-stick frying pan over medium heat.
Sear the steak in single layer batches until browned; transfer to a separate plate and set aside until all batches are done.
Melt the remaining butter in the pan; add the onions and sauté until transparent, then add the garlic and fry until just fragrant (about 30 seconds). Add the mushrooms and cook until the mushrooms are tender and cooked through (about 4 minutes). Mix in the mustard and paprika.
Add the wine and cook for about 3 minutes while stirring occasionally to mix all of the flavors through, deglazing the pan while scraping any browned bits off the bottom of the pan with your spoon. Allow wine to reduce down to about half the amount (about 3 minutes).
In separate pan, melt 1/2 Tbs butter and sprinkle flour over to make roux. Cook slightly, then add Worcestershire sauce and broth, whisk till smooth then add to mushroom mixture, mix well and bring to a simmer for about 5 minutes, stirring occasionally until the sauce begins to thicken.
Return the beef and any juices from the plate to the pan and season with any extra salt and pepper (if desired). Reduce heat down to low and mix in sour cream. Heat until hot (do not boil).
Plate egg noodles and spoon stroganoff over. Garnish with parsley.