Because of its delicious and decisive flavor, the mushroom is my favorite of all the stocks.
You can start preparing it while preparing the mise an place for any recipe in which you want to have the taste of mushrooms as your base ingredient and you will have it ready in minutes.
I love to use Porcino because it has an intense flavor that is easy to extract and use it in your recipes. However, you can make your mushroom stock with practically all mushrooms.
Prepare your bouquet garni using your favorite herbs. Just keep in mind to choose herbs that do not compete with the intense flavor of mushrooms (ex.: Rosemary).