Season and sear the beef: Pat the beef dry and season generously with salt and pepper.
Heat oil in a large pot or Dutch oven over medium-high. Sear the beef in batches until browned on all sides. Don’t crowd the pan.
Transfer to a plate.
Sweat the vegetables: Reduce heat to medium. Add onion, carrots, and celery with a pinch of salt. Cook 5–7 minutes until softened.
Add mushrooms and cook 3–4 minutes more until they release their juices and start to brown.
Add garlic and tomato paste: Stir in garlic and tomato paste. Cook 1–2 minutes, stirring, until the paste darkens slightly and smells sweet.
Deglaze and build the broth: Pour in a splash of broth to loosen browned bits, scraping the bottom of the pot. Add the remaining broth, bay leaves, thyme, parsley, and Worcestershire sauce.
Return the beef and any juices to the pot.
Add the barley: Stir in the rinsed barley. Bring to a gentle boil, then reduce to a simmer.
Simmer low and slow: Cover partially and simmer for 60–75 minutes, stirring occasionally, until the beef is tender and the barley is plump. Add water or broth if it gets too thick.
Finish and balance: Remove bay leaves.
Taste and adjust salt and pepper. Stir in red wine vinegar or lemon juice to brighten the flavors.
Serve: Ladle into bowls, garnish with fresh parsley, and serve with warm bread or a simple side salad.