Put the porcini in a bowl with 250ml boiling water and leave to soak for 25 mins. Heat the oil in a pan and add the onion, carrot, garlic, rosemary and seasoning. Fry for 5 mins on a medium heat until softened. Drain the porcini, saving the liquid, and finely chop. Tip into the pan with the fresh mushrooms. Fry for another 5 mins, then add the stock, marsala or sherry, tomato purée, barley and strained porcini liquid.
Cook for 30 mins or until barley is soft, adding more liquid if it becomes too thick. Serve in bowls with parmesan sprinkled over, if desired.