Recipe adapted from The Balthazar Cookbook via Smitten Kitchen. [Recipe serves roughly 10 cups].
1 ounce dried mushrooms (porcini, morels, or shitakes)
1/2 cup olive oil
1 large bunch fresh thyme
1 large yellow onion, thinly sliced
1 1/2 teaspoons salt
1/4 teaspoon freshly ground pepper
1 pound white button mushrooms, cleaned and thinly sliced
1 pound shitake mushrooms, stemmed, cleaned, and thinly sliced
6 cups low-sodium chicken stock
1 cup heavy cream
2 tablespoons unsalted butter
In a small bowl, soak the dry mushrooms in 1 cup of warm water for 20 to 30 minutes. Remove the reconstituted mushrooms and reserve. Pass the liquid through a coffee filter and reserve the filtered liquid as well.
In a large heavy bottomed pot, heat the olive oil over a medium low heat. Once heated, bundle your fresh thyme using some twine, and then add to the oil for a minute to infuse the flavor. Add the onion, garlic, salt, and pepper and cook for 5 minutes over medium heat. Turn the heat to high, and then add the fresh mushrooms. Cook for 10 minutes, or until almost all of the liquid has evaporated. Add the chicken stock, dried mushrooms, and filtered mushroom water. Bring to a boil and then reduce to a simmer. Continue simmering for 30 minutes.
Reduce the heat to low, remove the fresh thyme, and add the heavy cream and butter. Using an immersion blender (or food processor in batches), purée until smooth.