Preheat oven to 425°F.
Place mushrooms on a baking sheet and drizzle with olive oil. Season with pepper and roast for 15-20 minutes, until softened.
Transfer to a blender (reserving 1 tablespoon of mushrooms for garnish), along with 1/2 cup stock and purée until smooth.
Meanwhile, in a medium sauté pan, heat 1 tbsp olive oil over medium heat. Add shallot and cook until softened, about 5 minutes. Season with salt and pepper. Add garlic and thyme and cook for another 1-2 minutes.
De-glaze pan with wine and cook for 1-2 minutes. Stir in flour until incorporated, about 2 minutes. Add puréed mushroom mixture to pan, along with remaining 1 1/2 cups stock and cream to bring to a boil. Reduce heat to medium-low and simmer for 10-15 minutes until soup is thickened and warmed through.
Top with reserved mushrooms and a sprig of thyme and serve warm.