Mushroom Stock

This recipe is adapted from one found in How to Cook Everything Vegetarian by Mark Bittman.  It is a flavorful stock which is perfect of soup or any mushroom based rice dish. 

2 tablespoons olive oil
1 small onion, sliced
2 carrots, chopped
2 celery stalks, chopped
salt and pepper to taste
1 pound white mushrooms quartered
1 ounce combination of dried mushrooms
10 to 20 stems of parsley with leaves
2 quarts of water

1. Put half the oil in a large stock pot over medium heat.  When hot, add the onion and cook, stirring occasionally until the onion is soft.  Add the carrots and celery and sprinkle with salt and pepper.  Cook, stirring until the vegetables are tender, about 10 minutes.  Remove the vegetables with a slotted spoon. 
2. Put the remaining oil in the pan, when the oil is hot, add the white mushrooms.  Cook, stirring until the mushrooms are browned and have released their juices, about 10 minutes.  Sprinkle lightly with salt and pepper.  Add in the dried mushrooms and the reserved vegetables.
3. Stir in 2 quarts of water, and the parsley.  Bring to a boil, then reduce the heat so that the stock is bubbling vigorously.  Cook, stirring once or twice, until the vegetables are very soft and the stock has reduced, about 1 hour.  Strain in a colander, and use or store.