01 - Warm the olive oil and butter over medium heat in a large pot. Add the chopped onion, diced carrot, and celery, cooking for 5 minutes until vegetables soften.
02 - Incorporate the minced garlic and sauté for 1 minute until fragrant.
03 - Add the sliced mushrooms and cook for 8 to 10 minutes, stirring occasionally until browned and moisture evaporates.
04 - Pour in the white wine if using, and simmer for 2 to 3 minutes until mostly reduced.
05 - Add the vegetable broth, thyme, bay leaf, salt, and pepper. Bring to a boil, then lower heat and simmer uncovered for 15 minutes.
06 - Remove the bay leaf. Blend the soup with an immersion blender or in batches until smooth or to preferred texture.
07 - Stir in the heavy cream and heat gently for 2 to 3 minutes. Adjust seasoning as needed.
08 - Serve hot, garnished with fresh thyme leaves.