Sprinkle beef fairly generously with kosher salt and pepper. If you own this awesome slow cooker, where you can brown meat right in the slow cooker - add the oil to the slow cooker and then brown the beef right in the slow cooker, searing beef on all sides. Otherwise use a large skillet over medium-high heat to heat the oil and then brown the beef. Drain off fat. If using a skillet, transfer beef to slow cooker. You will need a large slow cooker for this recipe, as it makes a big quantity (ours is a 7-qt. size).

Add mushrooms, carrots, garlic, potatoes, onion, beef broth, wine, tomato paste, mustard, and thyme, and stir well to incorporate. Then stir in barley and add the bay leaf. Cover and cook on high for 4 hours. Then turn heat to low and cook for 2 hours more, or until beef is tender. Serve hot, with fresh parsley sprinkled over the top. A good, crusty bread for dipping is always welcome.