01 - Melt the butter with olive oil in a large pot over medium heat.
02 - Add onions, carrot, and celery; cook for 5 minutes until softened.
03 - Stir in minced garlic and cook for 1 minute until fragrant.
04 - Incorporate mushrooms and cook 8 to 10 minutes, stirring occasionally until juices release and browning begins.
05 - Pour in white wine if using; cook for 2 minutes until mostly evaporated.
06 - Mix in thyme, bay leaf, salt, and pepper.
07 - Add vegetable broth, bring to a simmer, cover, and cook for 15 minutes.
08 - Remove bay leaf. Puree soup using an immersion blender or in batches with a countertop blender, then return to pot.
09 - Stir in heavy cream and heat gently until warm. Adjust seasoning to taste.
10 - Ladle hot soup into bowls and garnish with fresh thyme and cream drizzle if desired. Serve with crusty bread.