In a large skillet, brown half meat in oil. Add salt and pepper. Repeat with the remaining beef. (I used a non-stick skillet and didn't use oil). Set aside in the crockpot and sprinkle with barley.
In the same skillet, brown carrots, celery, mushrooms and onion. Add more oil if needed. Add salt and pepper. Add garlic, Dijon mustard and cook about 2 minutes. Deglaze with the wine and add chicken stock. Bring to boil and pour in the crockpot.
Cook around 5 hours at low heat or 3 hours at high heat until meat is easy to tear with a fork. Sprinkle with parsley. Adjust seasoning.