In a large pot or dutch oven, melt butter over medium-high heat.
Sprinkle the meat with some salt and pepper to taste; add to the pot and give it a quick sear, 1-2 minutes on each side.
Using a slotted spoon, transfer meat to a bowl; keep warm.
Add the mushrooms, onion, and garlic to the pot; saute until the vegetables have softened, about 3 minutes.
Season with a touch of salt and pepper.
Stir in the tomato paste and Worcestershire sauce.
Pour in the beef stock; bring to a boil.
Add in the dried noodles. Reduce heat to a simmer and cook for 5-7 minutes until al dente.
In a bowl or large measuring cup, combine the sour cream and flour.
Whisk in 1 cup of the hot soup until combined; pour mixture back into the pot.
Cook and stir for 1-2 minutes to thicken.
Add the seared meat back to the pot and simmer for a few more minutes to cook through.
Taste, and adjust seasoning with a little more salt and pepper, if necessary.
Serve in individual bowls with some fresh chopped parsley.
