- 4 tablespoons unsalted butter
- 3 tablespoons extra-virgin olive oil
- 1 medium onion, finely chopped
- 3 garlic cloves, sliced
- One 1 3/4-pound head of cauliflower, cut into 1-inch florets
- 1 1/2 teaspoons ground coriander
- Salt and freshly ground pepper
- 4 cups vegetable stock or water
- 1 large egg
- 1 1/2 teaspoons cornstarch
- 1 cup plain low-fat Greek yogurt
- 2 tablespoons coarsely chopped cilantro
- Crushed red pepper, for sprinkling
In a large saucepan, melt 2 tablespoons of the butter in the olive oil. Add the onion and garlic and cook over moderate heat until softened, about 5 minutes. Add the cauliflower and coriander and season with salt and pepper. Cover and cook for 5 minutes, stirring occasionally. Add the stock and bring to a boil. Cover and simmer over moderate heat until the cauliflower is softened, about 15 minutes. Puree the soup with an immersion blender until smooth. Alternatively, puree the soup in a blender.
In a medium bowl, whisk the egg with the cornstarch. Whisk in the yogurt. Whisk the mixture into the soup and bring to a boil over moderate heat, whisking constantly until slightly thickened, 2 to 3 minutes. Season with salt and pepper and stir in the chopped cilantro.
Meanwhile, in a small skillet, melt the remaining 2 tablespoons of butter. Cook over moderate heat, swirling the pan occasionally, until the butter is fragrant and the milk solids begin to turn brown, about 5 minutes. Ladle the cauliflower soup into shallow bowls and drizzle the brown butter on top. Sprinkle with crushed red pepper and serve immediately.