Clean and slice the mushrooms evenly. Set aside a handful for garnish if you like, as they add a nice texture to the final soup.

In a soup saucepan over medium heat, melt the butter. Add chopped onions and garlic, and sauté until fragrant and soft. Add mushrooms and cook until golden.

Sprinkle flour over the mixture and stir well to coat the mushrooms. To get rid of the taste of raw flour, cook for two minutes.

Slowly pour in chicken or vegetable broth while stirring. Bring to a low simmer and cook until the mushrooms are soft, about 20 minutes.

Puree the soup in an immersion blender until it’s creamy and smooth. Alternatively, carefully transfer to a blender in batches.

Pour in heavy cream and stir. Season with salt, pepper, and thyme. Simmer until thick and silky, about 5 more minutes.

Ladle the soup into bowls, garnish with sautéed mushrooms or fresh herbs, and serve warm with crusty bread.