I had the most delicious Mushroom and Parmesan Soup at a restaurant and looked for a similar recipe. This pretty much was spot-on! Yum!
3 TBS extra-virgin olive oil
2 large shallot, minced (I used 1/4 cup grated onion and a pinch of garlic powder)
12 oz white mushrooms, trimmed and thinly sliced
7 oz shiitake mushrooms, stemmed and thinly sliced
1/4 tsp dried thyme
Freshly ground black pepper
2/3 cup dry sherry
4 cups low-salt chicken broth
2 cups water
3 oz finely grated Parmigiano-Reggiano (finely grate using a rasp grater)
1/2 cup crème fraîche, sour cream or plain Greek yogurt
4 tsp thinly sliced fresh chives
Heat the oil in a 4 quart saucepan over medium heat. Add the shallot (or onion) and 1 tsp salt and cook, stirring, until beginning to brown at the edges, about 3 to 4 minutes. Add the mushrooms, thyme, 1 tsp salt and 1/2 tsp pepper. Increase the heat to medium high, and cook, stirring, until the mushrooms soften and start to brown, 3 to 5 minutes. Add the sherry and cook, stirring, until reduced by half, about 2-3 minutes. Add the broth and 2 cups water; bring to a boil. Reduce the heat and simmer for 5 minutes. Stir in the Parmigiano and let cool briefly.
Working in batches, purée the soup in a blender until smooth. (I used an immersion blender). Transfer back to the saucepan and reheat.
In a small bowl, mix the crème fraîche, chives, and 1/4 tsp black pepper.
Season the soup to taste with salt and pepper and serve topped with a swirl of the crème fraiche.