Heat olive oil in a large pot over medium heat. Add the sliced leek and sauté for 5-7 minutes until softened.
Add the mushrooms to the pot and cook for an additional 5 minutes until they begin to release their moisture.
Pour in the broth and bring to a simmer. Let it cook for 15 minutes, allowing the flavors to combine.
Blend the soup with an immersion blender or in batches in a countertop blender until smooth.
Stir in the cream and season with salt, pepper, and thyme. Cook for an additional 5 minutes.
Serve warm with a drizzle of cream or a sprinkle of fresh herbs.