Preheat the oven to 180 degrees C. Soak the mushrooms in 1 cup of boiling water in a small bowl for 15 minutes, or until rehydrated and softened. Drain, reserve the liquid and coarsely chop the mushrooms (discarding any tough stalks).
Meanwhile, heat the oil in a large flameproof casserole dish over a moderate heat, add the beef and brown it all over. Add the carrots and celery to the dish.
Combine the mushrooms and their soaking liquid, the tomatoes, wine or stock, tomato paste, garlic, sugar and oregano in a jug, then pour into the casserole dish. Season with salt and freshly ground black pepper, then bring to the boil over a moderate heat.
Cover the casserole with a lid and put it in the oven to bake for 1 1/2 hours, or until the meat is tender.
Allow to rest for 10 minutes, then lift out the meat and carve into slices. Serve with the vegetables and sauce.