Season the beef pieces with salt and pepper. Heat a skillet over medium heat and brown the beef on all sides, then transfer it to the slow cooker.
Add the onion and garlic to the same skillet and cook until the onion softens. Scrape the mixture into the slow cooker.
Add the mushrooms, beef broth, Worcestershire sauce, paprika, and flour to the slow cooker. Stir everything together until the flour is no longer visible.
Cover and cook on low for 8 hours, until the beef is fork-tender.
Turn off the heat and stir in the sour cream until the sauce is smooth.
Serve the stew over the cooked egg noodles.