01 - Melt butter in a large pot over medium heat. Add finely chopped onion and celery; sauté for 3 to 4 minutes until softened.
02 - Incorporate minced garlic and cook for 1 minute until fragrant.
03 - Add sliced mushrooms and cook, stirring occasionally, for 8 to 10 minutes until most liquid evaporates and mushrooms turn golden.
04 - Pour in dry white wine, if using, and simmer for 2 minutes to reduce slightly.
05 - Add vegetable stock, fresh thyme leaves, and bay leaf. Bring to a gentle boil, then reduce heat and simmer uncovered for 15 minutes.
06 - Remove bay leaf. Use an immersion blender to purée the soup until smooth, or leave some texture as preferred.
07 - Stir in heavy cream and season with salt and black pepper. Heat gently for 2 to 3 minutes without boiling.
08 - Ladle soup into bowls, garnish with a drizzle of cream and fresh thyme sprigs. Serve immediately.