Begin by wiping the fresh mushrooms with a damp cloth to remove any dirt. Slice them thinly and set them aside.

In a large, heavy-bottomed pot, heat olive oil and butter over medium heat. Once the butter is melted, add finely chopped onion. Sauté for about 3-4 minutes until translucent, then stir in minced garlic and cook for another minute.

Add the prepared mushrooms to the pot, stirring well to coat with the onion and garlic. Cook for about 5 minutes until mushrooms soften and turn golden brown.

Stir in dried thyme along with salt and pepper to taste, mixing thoroughly to combine the flavors.

Pour in vegetable or chicken broth, bringing to a gentle boil. Once boiling, reduce heat to low and let it simmer uncovered for 20 minutes.

After 20 minutes, use an immersion blender to puree the soup until smooth, or leave some mushroom pieces intact for a chunkier texture.

Stir in heavy cream, warming gently over low heat without boiling. Taste and adjust seasoning as needed.

Ladle the soup into bowls, garnishing each serving with a sprinkle of freshly chopped parsley.