Most creamy mushroom soups have exactly that — cream — in them. In an effort to create a full-flavored, hearty soup that is both rich and creamy, without the addition of any wine, milk, or cream, I had to think carefully about the ingredients I was going to use.
Choosing good-quality, flavorful, and fresh mushrooms at the market was key. I had very fragrant hen of the woods mushrooms to use, and the meaty texture helped give the soup body. Instead of wine, I bolstered the flavor with a bit of agave syrup and a dash of soy sauce. While I used chicken stock, for added flavor, you can use vegetable stock instead for a vegan/vegetarian soup. I also included a bit of flour as a thickener, but it is not necessary, so leave it out if you want a gluten-free dish.
In a large saucepan over medium-high heat, add the olive oil. When shimmering, add the onion, carrot, and garlic. Sauté until translucent, about 8 minutes.
Add all the mushrooms and season with salt and pepper. Cook for 4 minutes, then add ½ cup chicken stock. Cook until the mushrooms are tender, about 6 minutes. Add the rest of the stock and the flour and bring the mixture to a boil. Reduce to a simmer and cook over low heat for 15-20 minutes, until the mushrooms are tender.
In a blender or with an immersion blender, purée the soup until smooth. Add the agave syrup and soy sauce and stir well. Add additional seasonings, to taste.
While hot, serve in bowls and garnish with prosciutto and spinach*, if desired. Serve immediately.
*Note: While I served the soup with a garnish of proscuitto and a spinach chiffonade; you could also try a dollop of sour cream, candied walnuts, and chives, or crisp bacon lardons and minced parsley.