Add the butter to a large Dutch oven set over medium heat. Liberally season the stew meat with salt, pepper & a pinch of garlic powder. Add it to the pot once the butter's melted.
Allow the meat to sear & brown on all sides, stirring just when necessary, so that it locks in the juices- the goal is NOT to allow the meat to cook through. Transfer the browned beef to a waiting plate & set it aside.
Add the olive oil to the Dutch oven along with the onions. Cook them, stirring often, until soft.
Add both the minced garlic & the sliced onions, stirring & cooking for 5 minutes.
Add the broth, wine, Worcestershire, thyme, bay leaf, and beef to the pot. Scrape up any browned bits that have stuck to the bottom of the pot, and stir everything together until evenly combined.
Bring the soup to a boil, then immediately reduce the heat to a gentle simmer. Cover the Dutch oven & let it simmer for 40-45 minutes.
In a small bowl combine the cornstarch and water, whisking together until evenly combined to form a slurry. Pour this into the soup, and stir until the soup's thickened slightly.
Turn off the heat and allow the pot/soup to sit & rest for 5 full minutes.
Add the sour cream to a small mixing bowl. Pour in 1/3 cup of the hot soup broth, and whisk quickly until the mixture's smooth & evenly combined. Transfer the prepared sour cream into the soup pot, and whisk it in quickly until evenly combined- this will prevent curdling.
Fish out the bay leaf. Discard.
Serve the soup by ladling it into soup bowls over the desired amount of egg noodles.