2. Strain liquids through a fine strainer and set aside. Chop porcini and set aside.
3. To cook the mushrooms, melt 2 tablespoons of the butter with the oil and saute the chopped mushrooms quickly over high heat until they release some liquids.
4. Stir in the chopped porcini and their liquids. Season with salt and pepper and set aside.
5. Bring the stock to a boil and then reduce heat, partially cover and hold at a simmer.
6. Melt 3 tablespoons of the butter in a large saute pan with high sides over moderate heat. Add the onion and cook for about 8 to 10 minutes, until the onions are tender and translucent.
7. Add salt and the barley and stir until the grains are coated with butter.
8. Add the hot stock and stir over low heat until the stock is absorbed. Cooking time may be as long as 30 minutes, depending upon the age of the barley.
9. During the last 10 minutes, stir in the cooked mushrooms, the chopped porcini and their liquids. Simmer until barley is tender, then adjust seasoning. Serve hot.