Using a mix of fresh and dried mushrooms and adding the mushroom soaking liquid gives this soup great depth of flavor. If you have a vitamix, use it here as it yields an incredibly creamy soup.
1 ounce dried mushrooms, such as shiitake, morel, or chanterelle
4 tablespoons butter
6 medium leaves fresh sage
¾ pound mixed mushrooms (such as cremini, oyster, chanterelle, or button)
4 garlic cloves, thinly-sliced
1 small yellow onion
2 medium leeks, thinly-sliced
2 cups chicken (or vegetable) stock
salt and pepper, to taste
lemon juice, to taste
1. Cover dried mushrooms with 2 cups boiling water and set aside for 20 minutes.
2. While the mushrooms soak, heat butter in a large dutch oven over medium-high heat. When the butter just starts to brown and smell nutty, add the sage leaves, fresh mushrooms, and a generous pinch of salt. Cook over high heat until the mushrooms release their liquid, the liquid evaporates, and the mushrooms begin to brown (depending on the size of your pot, this will probably take around 20 minutes).
3. When the liquid has evaporated, add sliced garlic and sauté 1 minute.
4. Add onion, leek, and a generous pinch of salt. Stir to mix everything together, turn the heat to medium-low and cook, partially covered, for 10 minutes.
5. Scoop the dried mushrooms out of their soaking liquid and strain the liquid through a fine mesh sieve to remove any grit.
6. Add chicken stock, reserved mushroom liquid, and reconstituted dried mushrooms to the pot. Season with another generous pinch of salt and a few grinds of black pepper. Bring mixture to a boil, reduce to a gentle simmer, and cook another 20 minutes.
7. Use a high-powered blender to purée the soup. Season with salt and pepper to taste, and finish with a squeeze of lemon juice just before serving.