Sauté the Aromatics: In a medium saucepan, melt butter or heat olive oil over medium heat. Stir in onions and garlic and cook until soft and fragrant.
Add the Mushrooms: Add your sliced mushrooms to the pan and cook for 8 – 10 minutes, stirring occasionally, until soft and browned.
Pour in the Broth: Pour the broth into the pan. Simmer for a further 5–7 minutes.
Blend the Soup: Blend the soup until it’s as smooth or chunky as you prefer with an immersion blender. You can also blend the mixture in a regular blender in batches.
Stir in Cream and Cheese: Reduce heat to low. Stir in heavy cream and cream cheese. Whisk until the cheese completely melts and the soup is creamy and silky.
Season and Serve: Season with salt, pepper and thyme, to taste. Let stand for 5 minutes, then ladle into bowls. Sprinkle with fresh parsley, if desired.