01 - Heat butter and olive oil in a large pot over medium heat. Add the onion and cook for 3-4 minutes until translucent.
02 - Add garlic and cook for 1 minute until fragrant.
03 - Stir in the sliced mushrooms and thyme. Cook for 7-8 minutes, stirring occasionally, until mushrooms are golden and softened.
04 - Pour in the white wine to deglaze the pan and let it evaporate for 1-2 minutes.
05 - Add the bay leaf and vegetable broth. Bring to a boil, then reduce heat and simmer for 15 minutes.
06 - Remove the bay leaf. Using an immersion blender (or in batches in a stand blender), blend the soup until smooth or leave a few chunks for texture, as desired.
07 - Stir in the heavy cream, and season with salt and pepper. Warm through over low heat for 2-3 minutes.
08 - Ladle into bowls, garnish with extra thyme and chopped parsley if desired. Serve hot.