Arrange onion and mushrooms in slow cooker and place beef on top of vegetables.
Combine broth with Worcestershire and garlic and pour over beef and vegetables.
Cover and cook on High 4 to 6 hours or Low 8 to 10 hours or until beef is very tender. Remove beef and let rest 15 minutes. Thinly slice or shred beef.
Arrange sliced beef on rolls and top with onions and mushrooms. Top each sandwich with 2 slices of cheese and place in 350°F oven for 2 to 3 minutes or until cheese is melted. Serve with au jus for dipping.
Recipe Notes
Notes: Serve without bread for a keto friendly meal. Serve over mashed cauliflower or cauliflower rice.