Season the beef chunks with salt and pepper.
In a skillet over medium heat, sauté onions until translucent; add minced garlic and cook for another minute.
Brown the seasoned beef in the same skillet until golden on all sides.
Transfer the beef, onions, garlic, and sliced mushrooms to a slow cooker.
In a separate bowl, whisk together beef broth, Worcestershire sauce, Dijon mustard, and additional seasonings; pour over the meat mixture.
Cook on low for 6-8 hours or on high for 3-4 hours until beef is tender.
Serve hot over egg noodles or rice with a drizzle of sour cream.
