Place porcini in a small bowl and cover with hot water. Soak for at least 20 minutes, or until you're ready to make the soup. Drain through a sieve lined with a damp paper towel, reserving liquid. Check porcini and rinse off any grit.

Place oil in a heavy-based pot set over moderately high heat. When oil is hot but not smoking, add chuck steak and brown all over. Remove from pan and set aside. Add onion, carrot and celery to pan and cook for 10 minutes, or until browned and softened, stirring frequently.

Add porcini and button mushrooms, then cook for 8 minutes, stirring occasionally.
Stir in tomato paste, stock, water and porcini soaking liquid. Bring to a boil, then add steak and simmer over low heat, with lid at an angle, for 1 hour.

Add barley and simmer for 40 to 60 minutes, or until barley and beef are tender, stirring from time to time. If soup becomes too thick, add some boiling water. Stir in dill, then cook for 10 minutes. Check seasoning and serve hot.