Preheat the oven to 400 °C. Toss the mushrooms with 1 tbsp olive oil, salt, and pepper. Arrange on a baking sheet and roast for 20–25 minutes, flipping halfway through, until golden.
Heat the remaining olive oil (and vegan butter, if using) in a large pot over medium heat. Add the onion and garlic. Sauté for 5–7 minutes until soft. Stir in smoked paprika and nutritional yeast, cooking for 1 more minute.
Add roasted mushrooms (reserving a few for garnish) to the pot. Pour in vegetable broth and bring to a boil. Reduce heat and simmer for 10 minutes.
Blend the soup using an immersion blender until smooth, or leave it slightly chunky by blending only half. Stir in plant-based milk or vegan cream. Season with salt and pepper.
Divide the soup into bowls. Garnish with reserved mushrooms, vegan cream, chili oil, and fresh herbs. Serve with crusty bread or a vegan grilled cheese.
