Mushroom Stock

• Olive oil, 2 tablespoons
• Yellow onions, 2 large, chopped
• Button mushrooms,

In a large saucepan over medium-high heat, warm the oil. Add the onions and sauté until lightly browned, about 15 minutes. Add the fresh and dried mushrooms, celery, and peppercorns along with 2½ qt (2.5 l