When it comes to making smooth, velvety vegetable soups, cauliflower is kind of a secret weapon. This brassica is low in overall fiber when cooked (compared to say, carrots or broccoli), making it ideal for smooth purees and sauces. In fact, this soup is so smooth and creamy that you’d be hard pressed to believe there isn’t any dairy in it. And to elevate this soup even more, we blend in toasted walnuts to thicken the soup slightly. The walnuts also provide richness, a background sweetness, and a pleasant buttery quality. For some textural contrast, we serve the soup with some pan-roasted cauliflower and plenty of extra toasted walnuts.