Cut the top sirloin strip steak into thin strips, making sure to trim any unwanted fat.
Coat the meat with enough flour to cover each piece evenly (about 1-2 Tbsp).
Heat a large skillet to medium-high and add the meat. Continue to flip the steak strips until the meat is evenly browned.
Remove the meat from the pan and add 3 Tbsp butter. Once melted, add the onions and mushrooms and saute for 3 minutes. Add the minced garlic clove and continue cooking for 1 additional minute.
Mix 1 Tbsp of flour into the vegetables and add white wine to the pan to deglaze it. Scrape all of the burnt bits off of the bottom, and allow the wine to reduce by half (around 2 mins).
Return the meat to the pan and add the beef broth. Reduce the heat to low and let simmer for up to an hour.
Boil water in a large pot and cook the egg noodles until fully cooked. Strain and set aside.
Add a small amount of the beef mixture into a small bowl and mix in ½ cup of sour cream. Once the cream is brought up to temperature stir it into the skillet.
Serve the beef mushrooms and onions over a plate of noodles, garnish with chopped parsley and enjoy!