Source : https://www.allrecipes.com/recipe/235589/chef-johns-creamy-mushroom-soup/

Ingredients :

• ¼ cup unsalted butter
• 2 (16 ounce) packages sliced fresh mushrooms
• 1 pinch salt
• 1 medium yellow onion, diced
• 1 ½ tablespoons all-purpose flour
• 6 sprigs fresh thyme, tied in a bundle with kitchen twine
• 2 cloves garlic, peeled
• 4 cups chicken broth, or more to taste
• 1 cup water, or more to taste
• 1 cup heavy whipping cream
• 1 salt and freshly ground black pepper to taste
• 1 teaspoon fresh thyme leaves for garnish, or to taste

Directions :

1. Melt butter in a large soup pot over medium-high heat. Sauté mushrooms and 1 pinch salt in the melted butter until mushrooms release their juices, 5 to 10 minutes. Reduce heat to medium-low and continue to cook, stirring often, until juices evaporate and mushrooms are caramelized, 15 to 25 minutes. Set aside a few attractive mushroom slices for garnish later, if desired.
2. Add onion to the mushrooms; cook until onion is soft and translucent, about 5 minutes.
3. Stir flour into the mushroom mixture and cook, stirring often, to remove the raw flour taste, about 2 minutes.
4. Add thyme bundle and garlic cloves, then pour in 4 cups chicken broth and 1 cup water. Reduce heat to low and simmer for 1 hour. Remove and discard thyme bundle.
5. Purée soup with a blender in batches until smooth and thick.
6. Stir in cream. If too thick, add a little chicken broth or water. Season with salt and black pepper.
7. Ladle into bowls, and garnish with reserved mushroom slices and thyme leaves.