01 - Heat butter and olive oil in a large pot over medium heat. Add onions and cook 3-4 minutes until translucent.
02 - Add garlic and thyme, sauté 1 minute until fragrant.
03 - Add sliced mushrooms and cook 8-10 minutes, stirring occasionally, until they release moisture and begin to brown.
04 - Pour in white wine and cook 2 minutes until mostly evaporated.
05 - Add vegetable broth, bring to gentle simmer, cover, and cook 15 minutes.
06 - Remove from heat. Blend with immersion blender until smooth or to desired consistency.
07 - Return pot to low heat. Stir in heavy cream and nutmeg. Season with salt and pepper. Warm gently 2-3 minutes without boiling.
08 - Ladle into bowls, garnish with chopped parsley, and serve hot.