Mushroom stock is a great accompaniment to beef and chicken dishes, and also serves as a way to quickly use any leftover mushrooms. It is easy to make and a large batch can be stored in the freezer for up to six months. This recipe yields approximately six cups of mushroom stock, and combines fresh and dried mushrooms for a stronger flavor. Use it in recipes or serve as a light side dish.
Heat the olive oil over medium heat in a heavy, 4-quart saucepan for 2 to 3 minutes. Meanwhile, clean the fresh mushrooms by wiping them with a damp cloth. Coarsely chop them and set aside.
Add the sliced onions to the heated olive oil, stir to coat and then add the salt. Saute for about five minutes, and then reduce the heat to low. Continue cooking for 20 to 25 more minutes, stirring frequently, until the onions caramelize.
Add the cooking wine and balsamic vinegar to the onions and bring the mixture to a simmer. Continue cooking for about 15 minutes, or until the liquid is reduced by half.
Add 6 cups of water, the garlic, thyme, pepper, and bay leaves. Stir to combine and continue simmering for an additional 20 minutes. Add the chopped fresh mushrooms and simmer for 15 more minutes, stirring occasionally.
Remove the pan from the heat and strain the mushroom stock through a fine-mesh strainer. Press the vegetables with the back of a spoon to extract all the liquid, and then discard.
Add the dried mushrooms to the stock and allow the mixture to steep while it cools. Cover and refrigerate overnight once the stock reaches room temperature.
Strain the mushroom stock again the following day. Use immediately or store leftovers in the freezer for later use. Store covered in the refrigerator if using within three days.