Label a gallon freezer bag with the name, date, cook time and note to add 4 cups broth after thawing. Add beef, carrots, mushrooms, onion, barley, tomato paste, Worcestershire, thyme, salt and pepper.
Press out air, seal, lay flat and freeze for up to 3 months.
Thaw completely in the refrigerator. Empty into a 6-quart slow cooker and pour in the cold broth, stirring once to loosen the tomato paste.
Cover and cook on low for 8 to 8 1/2 hours, until the beef and barley are tender.
At dinner, stir well, taste for salt and let the stew stand uncovered for 5 minutes before serving.