French Dip au Jus

Directions

1. Combine beef base and thyme; rub over roast and place in a 5-qt. slow cooker. Combine the onion, soy sauce, garlic, bay leaf and pepper; pour over roast. Add water.
2. Cover and cook on low for 8-9 hours or until meat is tender. Remove roast to a cutting board; cool slightly. Strain cooking juices, reserving onion; skim fat from juices. Discard bay leaf. Thinly slice meat.
3. To assemble sandwiches, spread mustard over bread. Top each bottom with three slices cheese; layer with beef, remaining cheese, mushrooms and reserved onion. Replace tops. Cut each loaf into four slices; serve with reserved juices.